Vista does not work at all with some wireless modems, e.g. Netgear.
Not true. Have a look at Netgear's list here:
http://kbserver.netgear.com/kb_web_files/n101649.asp
If you modem / router etc doesn't work with Vista a simple download of Vista compatible drivers will almost certainly fix the problem. Some old modems may not be supported, but this is fairly common and applies to other peripherals like printers, scanners etc and the same problem of lack of suitable drivers manifested itself when XP was launched in 2001. It's the responsibilty of Netgear to provide the drivers, not Microsoft, so if Netgear decide that it's not worth while expending resources in developing Vista drivers for some of their older products the blame should be laid at Netgear's door, not with Microsoft or Vista.
I've been using Vista Ultimate since it's launch at the end of January and wouldn't go back to XP.