Third party driver support for Wireless in Vista is a joke. Even top end Cisco gear has the same problem - dropped connections. It's not Vista's fault per se, although I started laughing when it landed on my desk in November and still haven't stopped.
Vendors are rapidly releasing new Vista drivers, so make sure you keep upto date.
Personally I wouldn't put Windoze on my machines if you paid me (well ok, depends how much). Unixman is right, any recent version of Linux can assign the MAC of its choice with a single command. This is regularly abused in wifi hotspots to hijack other peoples' paid for airtime.