Pros:
- Easier on DM's who don't have that much time.
- Monsters are easier to run without a substantial loss in variety.
- Easier to introduce to new players who want a game that is easier to play.
- Some nice ideas here and there.
- Combat less swingy (unfortunately, this usually results in combat grind where the result of the battle is known but still takes a while to play out).
- The game mathematics is very well balanced (sometimes annoyingly so).
- The DDI support is absolutely fantastic.
Cons:
- Black Box mentality to mechanics (flavour and mechanics therefore vary in how well they mesh - at times quite poorly).
- Combat duration has not been significantly reduced (although the number of rounds increases meaning players have more turns).
- All characters have the same powers mechanic (good for keeping playing levels equal, poor for making characters feel different).
- To run smoothly, you need minis, you need power cards, and you need things to indicate condition of the pieces involved. Tracking these conditions gets very fiddly otherwise.
- Some of the "good" complexity and option richness that was in the game has been sucked out of it. Characters tend to be a lot more standardized according to an optimal suggested build.
I suppose the crux is, a lot of people will read those cons and actually find them plusses. Those are the people that really dig 4E. For those that find them cons, 4E seems a step backwards rather than forwards.
Our group both jumped and was pushed into 4E. The current result is that our 4E game is still running (and enjoyably so from my own perspective). However, we have had one player quit the game (he absolutely hates 4E), we have another three (including myself) who prefer 3.x and we have 3 (including the DM) who like it. The end result however is that we are going back to 3.5 for a new campaign (while still running the 4E game here and there).
The thing to do is to try it with your group and see how it goes. Personally, I would have preferred a little more complexity in the game rather than the at times drastic streamling that has happened.
Best Regards
Herremann the Wise