I've played 4e and I'd play it again, if necessary.
However, for me it just wasn't necessary. I have a 3.5 game that I play in, and it's still going strong, and it's fun, so why stop having fun? And I started my own 3.5 game, and I got more players asking to play than I had chairs. I turned away a few people and now have my own game going strong. So 4th edition just hasn't been needed yet.
For my personal tastes, I like most of the things that 4e was trying to solve. Having to do character optimization or generally work to make a non-broken character? Yes, I like reading the books in my off-time. Having to juggle 4,000 spells that do unusual things that cannot be replicated by fighters? Yeah, I enjoy that. Having a 9 point alignment system? Love it.
There are two things I like about 4th edition that I'd like to put into 3rd edition. I like the combined skills, and I like that critical hits don't require a confirmation roll.
One of the things that I very much dislike about 4e is the definition of types such as defender & striker. I've deliberately not learned what those titles mean. I do not play any MMORPG, and never wanted those concepts to make an incursion into D&D. So when those words started getting explained, I flipped the pages until I got past that.
Also, 4e is too miniature heavy. I like the cover of 1e, which says something like "this game has no board, the action takes place in your imagination."