I got a chance to play a 4E game, and it was fine. And I will play again if given the chance. But it was not so good I would be willing to switch as DM at this point. I'm havng fun with 3.x, no one in my group wants to change, I have tons of material, I have electronic tools to help me prep. I'm set for now.
I might look at 4e as a source of some possibile house rules for some things that do look better (as opposed to merely different).
At some point, if a 3rd party publisher comes up with a product that a) focuses on the heroic tier (I'm not really interested in the higher end of the scale regardless of game or edition), b) shows me how I can remove certain 4E elements that I don't want to deal with (marking, bloody, low-level teleports, non-magical rapid healing) and how that affects other parts of the game, I could see myself being quite interested in that. From what I have seen, 4E is a pretty intricately balanced/interlocked set of rules. If I remove "bloodied" or marking, I could see it trickling down to other areas of the rules (what is a fair replacement if I take away marking powers from classes, what changes do I need to make to monsters, are there feats that should be removed or changed to accommodate that, etc.).
I also wouldn't mind seeing 3rd party rules for levels -1 and 0 (i.e. what happens or what is possible with PCs one or two levels less powerful than 4E's 1st level characters).