I've been involved, for example, in conversations recently about random encounters. In 4e, an encounter is a big enough investment that you rarely actually put your players through truly random encounters -- they might have encounters that "appear" random, but they're probably prepared encounters placed on the path the PCs will be traveling.
Yeah that's true fights in 4e can take too long. I actually do use random encounter tables in my current 4e game but the encounters tend to only half be fights, and those that are fights I tweak to make run quickly. It works fine but it definitely requires some outside of the box thinking and is not a all how the 4e combat rules work by default.
And that's a natural consequence of the encounter-as-setpiece shift in the game, but this (along with a bunch of other factors) tends to create game situations where we play through encounters, quickly narrate a bit of connective tissue, then play the next encounter.
I certainly can see that. I wonder why with my group that effect is minimal. I mean last session we had no real encounters and it was great fun.
Now, you've also shifted gears a bit -- roleplaying and improvisation are related, but they're not the same thing. Having a lot of pre-defined powers may very well lock players into a place where they see those powers as their only choices in an encounter, but I don't see that as the same issue/challenge as immersion, story, and roleplaying. Perhaps related, but not really the same thing at all.
Nope I haven't shifted, that's something I stated in my original post. Instead of arguing semantics, I've got another example...though YMMV and probably does
I created a 3D setpiece for the PCs' fight with a cranium rat hive mind; it was a fairly complex setup but made for a very dynamic fight. During the fight I role-played the hive mind extensively, but there was little to no roleplaying from the players. I even had some captured pixies for the pixie cavalier to free and hardly any roleplaying from him. Instead they focused on combat tactics, how to interact with the 3D terrain, asking questions about vertical movement minis in hand, taking cranium rat tokens off the map, scrambling to find any advantage thy could on their power cards/character sheets, rolling damage dice in glee, etc.
The game aspect totally swallowed any roleplaying coming from their end. It was fun, but the shift was very apparent.
Once combat was over the players shifted back into roleplaying again.
I intend to run a combat without map and minis next session to see if they'll be more engaged on the role-playing level, or whether it's just their preferred style to become like Sun Tzu when initiative is rolled.