I've been using Windows 7 beta as my primary OS for about a month now (or since whenever the beta first came out), and I've been very impressed with it. I liked (and still like) Vista, and Windows 7 seems to be Vista, but faster, more stable, and with more cool stuff. I never would've tried Vista on my single-core Athlon 64 machine, but Windows 7 runs as fast as (possibly faster than) XP on my machine, and it doesn't look like an 8-year old OS.
My sister has a white plastic MacBook (bought last summer), and while it's a nice machine, the only real advantage of OSX in my opinion is the iLife suite; while Windows photo gallery in Vista and W7 is alright, Movie Maker is a sorry excuse for a video editor.
One great aspect of Vista and Win7 which I haven't heard many people talk about is how Windows update actually gets drivers for your hardware. The first time I installed Vista, I was extremely impressed by how quick and easy it was; Windows Update offered me chipset and graphics drivers the first time I ran it. With XP, on the other hand, you can spend a day trying to find a driver for every damn piece of hardware; the ethernet won't work until you've installed the chipset drivers from that CD which "must be somewhere around here".