So far I'm really liking what I see in Win7. A long standing wish of mine has been that they go back and update some ancient things that have been with the system since, I dunno, Win95; the Calculator, WordPad and the abysmal Font management. I didn't think they'd actually ever get around to it, but both those apps have been refreshed and the font management is almost as good as on Mac, and 10 times better than in Vista.
I also like the fact that Win7 reads AAC and DivX files natively. The new Windows Media Player is much better than the disaster that shipped with Vista (WMP11). The taskbar and window management improvements are great for the most part, though I'm not digging the default layout with the bigass icons all aligned to the left, or how they jump around all over the taskbar if you enable text labels. Libraries is great too, but it's ridiculous that you can't include network shares in them (because those can't be indexed, as if I would care about that).
What I'd like to see in Snow Leopard, umm... other than the promised performance improvements there are some aspects of OS X that feel really dated. One is QuickTime, but it looks like they're taking care of that and implementing an interface similar to WMP12 with controls that overlap the video area and fade away when you release the mouse. Another thing in OS X that feels miserably dated is the Software Updates applet. Everything, from the stupid and overly enthusiastic globe (WOHOO! I FOUND AN UPDATE!!! I FOUND AN UPDATE!!! STOP EVERYTHING YOU'RE DOING AND DOWNLOAD THIS USELESS CAMERA RAW UPDATE NOW!!!) to the fact that it wants to reboot the system for nearly everything. I'd prefer it to be more like Windows Update in Vista/Win7, which installs everything silently except once every two months or so when it wants to reboot. And, more importantly, shows you a complete back log of everything you've installed. And finally, I'd like to be able to map a network drive permanently with extreme ease. Something is very wrong when a thing is ten times easier and more intuitive to do in Windows than in OS X.
Oh, and I'd like BootCamp to actually work. As long as it doesn't do fan control in Windows, and cripples firewire performance so much it's unusable for audio devices in Windows due to a bug in Apple's keyboard driver (sounds unrelated, but it's true), I'm holding off my purchase of one Mac Pro and one MacBook Pro 17"... if it doesn't handle Win7 like the best of PCs, I'm getting actual PCs...