Interesting discussion. I'm a D&D gamer and I have been playing 3.5 with one group of friends and 4th with another over the last year. I've a few thoughts about the way this has gone. I'm leaning towards 3.5 now but that's as much to do with the fact that my 4e crowd is having a hard time finding time to get together.
I like the 4e streamlining and I think the rulings of minions and cinematic combats are great. I love the way these flow, though they do tend to go on too long. This has caused me to think about how enemies handle encounters when it becomes clear they are going to lose - frequently the case for high hp enemies in 4e. This has actually lead to more roleplaying rather than less. It's also encouraged me to add mid-point complications to combats that make them more interesting. It's a very big change from 3.5 (my 3.5 party is 14th level and if a combat goes on beyond 2-3 rounds something very strange has happened!).
On the other hand I dislike the pure combat focus of the powers in 4e. In 3.5 I loved it when players used weird spells and magic items in the middle of combat. The casting times of rituals mean that non-combat spells will never come up during combat. I'm sure that as my players get more used to the rules they'll start to think a bit more laterally about their options, but right now they're still at the stage of looking at their at will and encounter powers and thinking that they are their only options in combat.
3.5 is getting tough to run at 14th level, but it's still good fun. I just have to make sure that there's only 1 real combat planned for any playing session because these slow things down remarkably. I'll certainly be looking over the Pathfinder rules to see if we should adapt our 3.5 game. I'll also continue to play 4e and I look forward to how the style of play changes as the group get more used to the rules.
I also find that roleplaying picks up as people get more familiar with the rules. FLicking through rulebooks kills the mood a little. I think we're getting back to it now, but there was certainly a dip when we picked up the new rulebooks.