I'm running Windows 7 Business on an HP NC6400, and it's pretty sweet. Out of the box, the only pieces that don't work are the SD Card reader and the fingerprint scanner.
I also have a super-sweet (to me, anyway) IBM Ultranav portable USB keyboard that has a Synaptics TouchPad (and TouchStick, which I don't really use) built in. It's nice not needing a traditional mouse on my desk.
Funny thing is that the TouchPad on the NC6400 works fine. But the TouchPad on the Ultranav doesn't. I tried the one from Lenovo (since IBM handed that off a couple of years ago). Turns out all I needed to do was to go to the Synaptics driver site and install the Vista driver.
Works like a champ.