I have really, really enjoyed my time so far with 4e. KotS, even poorly designed as the encounters and pregens are, was a breeze to run. My players had a great time (except my poor wife who simply could not roll above an 8 on a d20 for most of the three nights we worked on it before 6/6). I even had a player at the table who had never, ever played a table-top rpg in his life. I gave him a 10 minute basic rules introduction, he was kind of hesitant for about the frst 15 minutes, and then he was off and running like he'd been doing it for years.
A buddy of mine is running a beer-and-pretzels style game that's more testing out the system than anything long-term, but that's been very fun as well.
Unfortunately, I'm so disheartened by the GSL that I may take a pass on the rest of 4E. Doubtless, we'll play with the 3 core books we have, but I'm going to have to give a long, hard think before I give any more money to WotC.
I understand their motives, or at least what I assume to be their motives, and I don't think it's unfair of them to do what they've done, or dishonest, or whatever. I think it's patently foolish. I think it's bad for the industry, bad for consumers, and will ultimately prove to be bad for WotC. If WotC got nothing else out of the OGL-era, the third party publishers provided a way for WotC to scout (relatively risk free) for the best talent in the industry. That alone is worth the very minimal sales losses that might have resulted from True20, Spycraft, et al.