From what I've seen with the fourth edition, they could have just kept 3.5 and added a few improvements. I don't like the fact that there are few spells, but I do like how a wizard can cast a spell over and over again. I think that WOW has influenced this version of D&D and they have tried to make the game more hack and slash like that game is. One of the charms of 3.5 is the fact that someone can become good at something other than killing, like picking pockets to the exclusion of other things. This is more realistic in my view. By simplifying the rogue so that one is about equally as good in everything is a step backwards in my opinion. I'm not planning to update my collection, but I might make some more house rules to improve the 3.5 system that I do have.
Mike