You know, it's really interesting to see the opinions of everyone that has replied so far. Unlike previous edition discussions, I really can;t find more than an ounce or two of vitriol in the whole batch, which is really good. Is this a sign of this generation of gamers maturing, or just an attitude of acceptance as a whole?
As someone who has played since '78, it always irks me when a new edition or change is touted and trotted out; but eventually, I get on board and see why these changes were made and how it advances the hobby as a whole. I think 3rd edition (and 3.5) was the natural progression in the line but 4th is going to be a compromise of getting back to our roots (less rules/rules lighter (not light)) and moving forward with progressive ideas (Vancian magic being face-lifted for example.)
There are very few 'things' that make D&D what it is, but those that do, need to stay. AC, XP and HP or the big ones, I've played with defensive bonuses and life points and stamina and frankly, it just not as fun as my ol' HP/AC combo. and levels and XP, they are what makes D&D's archaic goodness. Outdated, yeah, but still usable. I haven't agreed with every change and often changes were made to better the game that failed miserably (CRs anyone?) but then the 'Player's Option' build rules (2E.7) weren't exactly my favorite either.
I could easily sit here and complain, but really, what good would it do? 4th edition is on its way and like its predecessors, 3.x will be forgotten by manufacturer's and clung to like a security blanket by a handful of fans. The system was a good attempt, but the changes that failed, well, its time to dump them. Change is inevitable, viva la revolution!