After playing and DMing 3e for a few years, I came to the realization that the target audience for 3e did not include me. Granted, I like most of what they've done in 3e, but the style of game I prefer is not what 3e offered. From what I've seen of 4e, WotC looks to be moving the game in a direction I prefer. I like most of the changes I've heard about. The reduction of the Christmas tree effect, the points of light assumption, and the revised resource management are my biggies. I also like the idea of wizard's implements. Since Mike Mearl's wrote The Quintessential Wizard, which had a chapter on Wizards' Staves in it, I guess I knew this was coming.
There are some I am skeptical about. While I like the new resource management system, I can understand why some people would not. Players who don't want anything to do with resource management (yes, they exist) will no longer have any simple hack'n'slash characters to play. My thoughts on wizard traditions are mixed. I think they add color to a wizard's background, but yet at the same time they can be seen as a straightjacket. You could probably say the same thing about clerics and gods, though.
My biggest concern is that some stuff that many players consider core will be moved to supplemental books, like the rumoured PHB2 and the possible splatbooks hinted at in the Israeli leak. I don't want to buy supplements to buy stuff I consider to be essential. I guess as some people complained about 3e "Heroizing D&D", some others will complain about 4e "White Wolfizing D&D".
Overall though, I am quite looking forward to 4e despite my reservations.
Howndawg