Does the 4th ed ruleset change the way you design adventures from how you may have done it before? I know that each edition has brought changes in the way published adventures are laid out, but that's mostly cosmetic.
Yes. I find it more useful to consider 4E a game of its own than "just the latest edition" of an existing game.
Lots of things have changed, enough that you can't simply take a 3E module and convert it on the fly.
* 4E combat needs plenty of room - previous edition maps rarely cut it
* 4E combat encourages exotic terrain features (the "playground" effect) - previous edition maps rarely cut it
* 4E combat is geared for bigger fights - while stumbling upon two lone Orcs presented some risk in 3E (if they got in a crit before they were killed), such an encounter comes off awfully flat and lame in 4E - there simply is no element of risk whatsoever
* 4E combat is about the status effects - this makes a fight against a lone monster suspectible to "stunlocking". First off, you can't use a regular monster of higher level as this often leads to unsatisfactory results (once the players get the upper hand, the rest of the fight turns into a dreadful grind where the players know they will win, it just takes them half an hour to grind down all the hit points). You get much better results if you lower the level of the monster (to perhaps four levels higher than the party, tops) and instead add more monsters. Note that using an Elite or a Solo monster counts as "adding more monsters" (adding one and four monsters, respectively).
The big change I notice is the reliance on multiple opponents for each encounter. Instead of simply stopping a troll that lives under a bridge, apparently now youre supposed to stop the Troll, his pet Hellhound, and his 4 Ogre Minions. (ok, its a silly mix - but you get my point)
Great you have found out about this already. The main underlying reason is monster roles. The fight simply becomes much more exciting and tactically interesting if the opposition consist of monsters with different roles. That's a huge help in avoiding the grind.
I would recommend being careful with Elites and Solos of the party's level or higher, basically because that means a fight with few or even just the one opponent. A fight against a Solo becomes much more interesting if the Solo gets to bring along half a dozen allies as well as a bunch of minions. The only way you can accomplish that (without a TPK) is if the Solo is of a lower level than the heroes.
Assuming you're making a standard "playable-in-an-evening-maybe-2" dungeon style adventure, is there anything else you need to take into account?
Any thoughts, or design tips that aren't in the 4e rulebooks?
I learn much faster by example than by reading up on rules.
Thus I can't recommend
Dungeon Delve enough. Taken at face value, it might look like just a bunch of unconnected dungeon bashes with no roleplaying potential.
But I see it as a collection of great examples on encounter building. (For more insight, check out the excellent review thread by Baz King over at rpg.net, where each delve is discussed and graded)
I wouldn't use the delves as-is. However, I will be slotting them encounters into my own (more story-laden) game.
(you can have that troll, you just need to make him tougher)
Aside from the possibility of using a Troll as a Solo, you could also just pick a higher level Troll.
Be careful with this. Just picking a single high level opponent (say, a monster five or seven levels higher than the party) doesn't work nearly as good as in previous editions.
Rolling dice becomes boring: the troll always hits, the party (nearly) always misses. Because of all the misses, the troll's high hp is made into an even larger heap of hp. Despite the troll mostly hitting, a single 4E creature simply doesn't cause all that much damage.
You can hopefully see that this leads to a drawn-out grindfest, where the PCs have ample time to distribute healing surges to ensure the Troll's efforts never translate into a really dangerous situation.
When it dawns on the players the fight has been reduced to a simple comparison between the Troll's hp and the total pool of healing surges (and their triggers) you will know you have failed to create an interesting fight. This phenomenon is completely new to 4E (to me at least).
Taken to its extreme, we get those endless discussions about "my Paragon dragon should be able to wipe out a party of Heroic player characters with a single Dragon Breath". The game simply doesn't concern itself with mismatched fights like that. (A heroic party stands no chance against a paragon tier Dragon, but it will still take a dozen rounds or more for the Dragon to kill off the PCs. This is not a big design flaw because? Because he game never promised to handle that kind of disparity.)
So don't use a higher-levelled Troll. Use a Solo Troll instead. And this is where you will realize the Monster Manual simply doesn't cut it. At least, it's my experience that you will often find that the MM gives you a rather narrow selection of critters each time you turn to it - because of the monster roles and because of the Minion/Elite/Solo divide. You want a level 8 Soldier? The MM gives you a selection of only four choices. And one of those choices is an Elite. And of the three remaining, one is a beetle swarm, one is an Angel, and one is a shadow warrior. I can imagine plenty of campaigns where that leaves you with only one choice that fits the adventure and setting, or even none.
But back to the Solo Troll. The DMG gives you the impression Solos are best used on their own. Don't buy that.
Rather than experimenting with a War Troll (L14), you could solo-ify a common Troll (L9) and give it several allies (perhaps a Dark Stalker and a dozen Troglodyte Warriors) for a satisfying encounter for a level 10 party.
Each solution has its advantages and disadvantages. The common thing is that "solo" fights are often not all that interesting, at least if the monster lacks options and reactive abilities that surprise the PCs or turn the way the battle is fought.
The best suggestion here is probably to pick or create a "non-boring" monster and/or add interesting terrain features.
Ayup.
Bigger encounter areas: What might have been the area for 3 encounters in 3E can be the area for one encounter in 4E - but still including all the monsters of the three 3E encounters.
Ayup.
Skill Challenges will be a nice tool to handle situations that you don't want to resolve with a single dice roll, but still want to be affected by the player characters actual abilities. There is a lot that can be done with them, and they can be expanded a lot, too (I am sure someone will bring up the "Obsidian" system described in the House Rules forum).
Let me just say that I've ignored SC's for now. They clearly do not work straight out of the box.
Note that this does not make the rest of the game less fun!