I installed Vista on my Dell D620 yesterday, and everything mostly worked out of the box. I just had to download drivers for the Nvidia quadro NVS 110m, but other than that no problems.
I think the wireless card didn't have drivers out of the box, but the lan did, which connected to windows update and downloaded drivers. But I didn't notice, it just seemed to happen in the background. Aero Glass is pretty cool.
I couldn't get cygwin to install properly, the postinstall scripts wouldn't run, complaining about bash.exe not working each time one of those scripts ran. Maybe Microsoft Services for Unix will install?
I'm surprised at the lack of gadgets for the sidebar. I'm missing a weather gadget, and a battery monitor.
Update: Ooops, I did something to break IE 7 Beta that comes with Vista. It won't respond after I enter a URL to visit. I was installing Outlook 2007 with Business contact manager beta, when this happened, and it turns out the cygwin stuff was also running in the background, amongst other stuff I had open. Firefox beta 2 is working fine however.