Hello all, I'm here to offer my opinion as a grognard who's been playing D&D since before the red Basic boxed set. So I'm a grognard in the time sense, not in the '3.x is the be all-end all and you'll have to pry those books out of my cold, dead, fingers' sense.
I bought KotS Tuesday night and have been reading it since then. Overall, I like what I've seen so far. There have been questions (which have been answered mostly in thanks to those on these boards) and there have been epiphanies as I put together a few important pieces of 4E tech and went "Wow! That's really neat!"
I had expected to like what I saw though, since most of what I've heard about 4E sounded good to me. The production value of the adventure could have been better, but the crunch of it's innards was satisfying. All in all, the reason I think I'll prefer 4E to 3.x is simply a matter of ease. My wife questions why I'm going to buy another whole new set of books when the old ones were good enough when they were new. Especially since it'll be a few years before they have enough books out to match all the options which are available now at the end of 3.x. My answer to her was that I believe I can have more fun playing this new system with less options(for now) than I can with that clunky system with more options.
This is my main reason for leaning towards 4E. It seems to fix what I felt were problems which cropped up due to the nature of the rules in 3.x. Just like I was hopeful towards 3E when reading about it at the end of 2E (when these boards were young and new

). Personally, I can't wait to play the adventure. But I think I'm going to hold off until I get the Core Book giftset that I preordered back in February (when I had tax-return money). Until then, I'll probably run a few combat tests to get more familiar with the rules I have and using the pre-gens for that. Once we have a PHB, we'll make up our own characters and then start into KotS.
So for me, 4E looks great so far, and I look forward to more and to getting to actually play it. For those that still prefer 3E and don't care for the new stuff, that's your perogative.
To each his own...