ok well i dont know about the 650+ but I do have the dwl 650 and the 520.
that being said they can be used under linux but are kinda of a pain.
I used the Wlan-ng drivers
www.linux-wlan.com and have also been able to get the cards up and running with the wvlan drivers from the pcmcia ebuild (although all i could do is ping couldnt connect)
the only painfull part i really came across is on the install of the wlan-ng drivers it asks for your pcmcia source dir and I havent the closest clue to wear that is right now.if anyone could help me with that id appreciate it. and hopefully I will be able to whip up a possible ebuild after i have my cards configured again ,it'll be my first one tho so dont expect much:).
/edit sorry if you have the k1 revision as i havent fiddled with those ,i believe my two cards are prism2 based . they are fairly new tho.