Many things I liked about Vista, usb support and no questions during the install, putting the cd key in later, more sensible folder layout, less blurry window movement. But sadly these were tarnished by things like ugly green stripes, performance problems, crappy drivers, software issues, and aggressive UAC. Improvements have come with the service packs, but too late to clear its reputation.
I'm happy to say that Microsoft have done a great job with Windows 7, it has the best bits of Vista, performance equal to XP, a refreshing style, less things to annoy you, and other little changes that make the whole experience pleasant.
Windows 7 works great even on my little Samsung NC10, so I expect it will become standard on netbooks after October. If your not getting your copy through work or piracy, consider buying now as Microsoft are doing pre-order discounts in various countries.