First as to the original topic:
1. Yay! Glad to see themes coming in a wide scale. Personally, I think they are a nice way to differentiate characters without making things too complicated.
2. Honestly, I think WotC is between a rock and a hard place here. Sure, some feats, etc. would be easy to handle (like the previously stated Weapon Expertise (Heavy Blade)). But many others are simply not good as opposed to obsolete. I think perhaps the goal should be to update the obsolete so that they at least read like the choice that obsoleted them (like Heavy Blade Expertise), while perhaps worrying about the options that are simply "not good" later (or perhaps throwing a "deprecated" tag on them).
3. Its nice to see them taking an honest look at their game (even if its just one person) and saying "Hey, this could have been implemented better." I think it reaffirms that they are at least trying to make the game better. Obviously one person's "improvement" is another's "step backward" but I do think WotC is trying to do the best they can, and Immediate Actions are certainly one area that can cause all kinds of headaches -- particularly when monsters have triggered actions it can really get crazy.
As for immediate actions in general, here's my experience. The ranger in the group I run tends to use Combined Assault (or whatever the Battlefield Archer power is called) at the first opportunity he gets. Its rarely designed to finish off a creature, or hit the creature that appears to be particularly problematic, etc. That being said, he also does not have Disruptive strike, so at least he's not simply trying to up his DPS. The Swordmage on the other hand has Dimensional Vortex (and another similar power that pushes the attacker -- can't recall the name), and often struggles with when to use it. For the most part though, she's resorted to waiting for either a) a crit, or b) a time when getting hit would cause the ally to drop. Of course, part of the problem the swordmage has here is that since they are immediate actions, they would prevent her from using her Aegis should a marked target attack an ally and she is often pretty good about marking a target and then backing away from it so that it cannot easily attack her.
Obviously each person's experience will vary but I think the idea behind what Mike is suggesting is that you wait for something "major" to happen in the battle to pop the interrupt. This is probably how they were initially intended, just not how they are always used. A single interrupt in and of itself isn't so bad, but as the PCs get to higher levels, the number of interrupts and triggered actions can really start to add up fast. I've seen situations where a single PC's attack resulted in three or four triggered/immediate actions and after resolving all of it we were like "Uhh, so who's turn is it again?" Obviously this was a rare case, but it was also in heroic, so I can imagine it getting worse in paragon and epic tiers.