We've primarily been a 3 and 3.5 E group through 2008. We played 3.5 and 4 in separate games until a few weeks ago, when my players narrowly voted 4E off of the island by a vote of 5-3 (Yes, I have 8 players). We had played a variety of 4E games, including the Scales of War AP, but they never really caught the imagination of the players (we had just done the skill challenge with the war council too, and they hated every minute of it).
Very recently, we got on the pathfinder wagon. the other DM started the Council of Thieves last summer, and when Scales of War died, I'm started running Legacy of Fire. So far, the group seems to be engaged again, though we will see about that.
During the debriefing after each failed game, the feedback was that the game was not organic, players felt that their abilities dominated their character sheet, and didn't provide them with the flexibility as a player that they were used to. They also found it hard to define their personalities, and that in a world without a well defined setting, they weren't able to get into character. I've always felt that my group walks a weird line between RP and hack-and-slash, and I thought that 4E would appeal to them.
Pathfinder is good for us going forward, so I find it unlikely that we'll be going back to 4E. I like the idea behind 4E, and it certainly is more simple to work with as a DM, but as a player, I think I do agree with my players. 4E is a nice diversionary game for a short series of sessions, but I'm not sure that I could play in it (run it, sure) for a long campaign.