Vista has a native command line version of Netstumbler. Sort of. I found out about in a SANS webcast. Ed Skoudis was talking about the activities at DefCon. At the end of the broadcast, he talked about some interesting projects he'd been working on, and he mentioned using Vista to natively war-drive. (Ed taught the SANS 504 class that I took. Highly, highly recommended.) A quick Google search turned up the following command:
netsh wlan show networks mode=bssidI put that in a shortcut file and it worked great. I believe Viststumbler sits on top of that command and provides a graphical interface. Viststumbler also has GPS capabilities, but I haven't explored it. Running Viststumbler at home showed me a bunch more networks than I initially thought were around.
So, if you're looking for a good wireless discovery tool like Netstumbler for Vista, I recommend Vistumbler.