The d20 styled skill checks have always bothered me since 3.0, because I was/am also a player of 7th Sea... a game system where there is no theoretical maximum you can roll because of the "exploding" die mechanic.
In a nutshell... to do anything, you'd roll a certain number of d10s (the die of choice for the system), and add them up to reach a target number. If any of those dice showed its highest value of 10, the die was said to "explode". You got to add 10 to your total, then pick it up and roll that die again adding its additional value to your total. If you were lucky enough to then roll a second 10, you'd add 10 to your total and then roll the die again (continuing ad nauseum so long as you kept rolling 10s). This mechanic meant there was never any target number the GM could set that wasn't theoretically possible to reach. As long as you kept rolling 10s, you could always get a higher and higher total.
I felt this was a great mechanic, because it made dice rolls even more exciting than normal. There was never any "ceiling" of possible target number to reach (unlike d20, where the best you can possibly do is 20 + skill mod). Even if a TN was exceedingly high and which might not normally be possible on the total amount of dice I was rolling... there was always that chance that one or more of my dice would explode... then I'd get to add and reroll those dice again.
That kind of excitement I personally find lacking in standard d20 skill checks (and always have, even since the advent of 3.0). There is most definitely a "hard ceiling" of target number. Either you can reach it with a d20 + skill mod, or you can't. Plus, since you only are rolling a single die and usually have calculated what you need to roll or higher prior to throwing it ("okay, the TN is 15 and I have a +6 skill mod, so I need a 9 or higher to make it"), there is much less drama in its rolling. The die drops, you read it, and you immediately know whether or not you were successful. For my money... the drama is much, much less compared to the drama I have felt in making these kinds of rolls in 7th Sea.
Thus, I decided several weeks ago to see if instituting a 7th Sea-styled skill roll mechanic would work with 4e and make skill checks and skill challenges more exciting. I adapted and amended the rules this way:
Everyone's skill mods are calculated as normal: ability modifier + 1/2 level. However, you do not add a +5 for a skill you are trained in (although we still have trained skills).
To make a skill check: roll three d6s added together, plus your skill mod. If any or all of the d6s you rolled shows a 6, you add them to your total and re-roll the die, adding in the new value to your total as well. If you roll another 6, you add it and reroll it a third time... and keep rerolling and adding so long as you keep rolling 6s. You have to reach a TN set by the DM, or beat the opponent in an Opposed check.
If you are Trained in the skill, you get to roll an additional d6 (i.e. 4) instead of the usual three. If you have taken the Skill Focus feat, you get to roll an additional d6 as well (meaning five d6s total).
And that's all there is to it.
The hardest part in all of this is deciding on target numbers for the challenges. My math-whiz player friend tells me that a 3d6 with re-rolled 6s averages out to a little more than 14 per roll. 4d6 with re-rolled 6s averages out to about 19 per roll. Thus (knowing that my 4th level players are usually adding an additional +2 to +6 to these skill rolls for their skill modifier), I start with an average TN of 18, then go up or down by three from there. So easy checks might be TN 15 or even 12, whereas harder checks might go to TN 21 or 24.
Thus far, things have gone very, very well. I definitely think my players find this method a little more drama-filled, because they have to search out where all three or four dice have landed, do some quick addition in their heads, plus hope/exalt when there's a 6 in the mix that they get to reroll. And the drama gets ramped up even higher when they are in an Opposed check and I hold off rolling until they've done theirs and added theirs up... then roll my NPCs dice in front of them. When *I* start dropping 6s down, they know there's a chance that I might be meeting or exceeding them on subsequent rolls and they get a little lump in their throat.
In the grand scheme of things, these are only dice rolls after all... so there's only so much excitement you can actually wring out of them. But I truly believe that the process of rolling many dice, adding dice together and the open-endedness of "exploding" dice makes what little we do have just a little bit more. For a game like this, any little bit helps.
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To answer a couple additional things... I only do this for skill checks, *not* for combat. Combat has its excitement built into it with hit points, AC, powers and the like. Exploding die rolls would just make things too complicated. But for skill checks/challenges, the exploding die system is great.
And for those of you familiar with the 7th Sea rules... yes, I do in fact also allow players to "call raises" on their target numbers (again, using numbers in batches of 3). So if a TN is 15 for example, they can voluntarily "call one raise" and make the TN 18 instead... and they will receive additional information if they succeed (or even more info if they called two raises, etc.)
This is especially great when doing skill challenges... because I let them call raises on easier TNs, to spend them to lower the TNs on their more difficult skill checks. So for example, our multiclassed paladin/ranger of Melora was trying to recall whether she knew any information about a location called the "Satyr's Glen". The check was going to be a Nature check, TN 24 (which, being trained in Nature, would be possible but not nearly assured). I first allowed her to make a History check to start with, starting with a base TN of 12. For every raise she called on her History check, if she succeeded, the TN of the Nature check would drop by 3. So she called two raises (to make her History check TN an 18), and succeeded on the roll... thus making her History check TN also an 18. She then succeeded on her Nature check (barely, rolling a 20), and got her information.
In a nutshell... to do anything, you'd roll a certain number of d10s (the die of choice for the system), and add them up to reach a target number. If any of those dice showed its highest value of 10, the die was said to "explode". You got to add 10 to your total, then pick it up and roll that die again adding its additional value to your total. If you were lucky enough to then roll a second 10, you'd add 10 to your total and then roll the die again (continuing ad nauseum so long as you kept rolling 10s). This mechanic meant there was never any target number the GM could set that wasn't theoretically possible to reach. As long as you kept rolling 10s, you could always get a higher and higher total.
I felt this was a great mechanic, because it made dice rolls even more exciting than normal. There was never any "ceiling" of possible target number to reach (unlike d20, where the best you can possibly do is 20 + skill mod). Even if a TN was exceedingly high and which might not normally be possible on the total amount of dice I was rolling... there was always that chance that one or more of my dice would explode... then I'd get to add and reroll those dice again.
That kind of excitement I personally find lacking in standard d20 skill checks (and always have, even since the advent of 3.0). There is most definitely a "hard ceiling" of target number. Either you can reach it with a d20 + skill mod, or you can't. Plus, since you only are rolling a single die and usually have calculated what you need to roll or higher prior to throwing it ("okay, the TN is 15 and I have a +6 skill mod, so I need a 9 or higher to make it"), there is much less drama in its rolling. The die drops, you read it, and you immediately know whether or not you were successful. For my money... the drama is much, much less compared to the drama I have felt in making these kinds of rolls in 7th Sea.
Thus, I decided several weeks ago to see if instituting a 7th Sea-styled skill roll mechanic would work with 4e and make skill checks and skill challenges more exciting. I adapted and amended the rules this way:
Everyone's skill mods are calculated as normal: ability modifier + 1/2 level. However, you do not add a +5 for a skill you are trained in (although we still have trained skills).
To make a skill check: roll three d6s added together, plus your skill mod. If any or all of the d6s you rolled shows a 6, you add them to your total and re-roll the die, adding in the new value to your total as well. If you roll another 6, you add it and reroll it a third time... and keep rerolling and adding so long as you keep rolling 6s. You have to reach a TN set by the DM, or beat the opponent in an Opposed check.
If you are Trained in the skill, you get to roll an additional d6 (i.e. 4) instead of the usual three. If you have taken the Skill Focus feat, you get to roll an additional d6 as well (meaning five d6s total).
And that's all there is to it.
The hardest part in all of this is deciding on target numbers for the challenges. My math-whiz player friend tells me that a 3d6 with re-rolled 6s averages out to a little more than 14 per roll. 4d6 with re-rolled 6s averages out to about 19 per roll. Thus (knowing that my 4th level players are usually adding an additional +2 to +6 to these skill rolls for their skill modifier), I start with an average TN of 18, then go up or down by three from there. So easy checks might be TN 15 or even 12, whereas harder checks might go to TN 21 or 24.
Thus far, things have gone very, very well. I definitely think my players find this method a little more drama-filled, because they have to search out where all three or four dice have landed, do some quick addition in their heads, plus hope/exalt when there's a 6 in the mix that they get to reroll. And the drama gets ramped up even higher when they are in an Opposed check and I hold off rolling until they've done theirs and added theirs up... then roll my NPCs dice in front of them. When *I* start dropping 6s down, they know there's a chance that I might be meeting or exceeding them on subsequent rolls and they get a little lump in their throat.
In the grand scheme of things, these are only dice rolls after all... so there's only so much excitement you can actually wring out of them. But I truly believe that the process of rolling many dice, adding dice together and the open-endedness of "exploding" dice makes what little we do have just a little bit more. For a game like this, any little bit helps.
**********
To answer a couple additional things... I only do this for skill checks, *not* for combat. Combat has its excitement built into it with hit points, AC, powers and the like. Exploding die rolls would just make things too complicated. But for skill checks/challenges, the exploding die system is great.
And for those of you familiar with the 7th Sea rules... yes, I do in fact also allow players to "call raises" on their target numbers (again, using numbers in batches of 3). So if a TN is 15 for example, they can voluntarily "call one raise" and make the TN 18 instead... and they will receive additional information if they succeed (or even more info if they called two raises, etc.)
This is especially great when doing skill challenges... because I let them call raises on easier TNs, to spend them to lower the TNs on their more difficult skill checks. So for example, our multiclassed paladin/ranger of Melora was trying to recall whether she knew any information about a location called the "Satyr's Glen". The check was going to be a Nature check, TN 24 (which, being trained in Nature, would be possible but not nearly assured). I first allowed her to make a History check to start with, starting with a base TN of 12. For every raise she called on her History check, if she succeeded, the TN of the Nature check would drop by 3. So she called two raises (to make her History check TN an 18), and succeeded on the roll... thus making her History check TN also an 18. She then succeeded on her Nature check (barely, rolling a 20), and got her information.
A feat I've never even remotely come close to doing before or since. To put it in these terms my dice exploded and I rolled six after six. 
Under the standard DnD skill system I could never have done that.
