FWIW, I've had no major problems using the D-Link DWL-122 with my G3 iMac running Panther.
It always connects to my WLAN properly and is plenty fast enough for what I do with it, despite the USB 1.1 bandwith limitation.
The only issue seems to be if I do a warm-reboot, the Mac doesn't recognise it after the reboot, but this can be resolved simply by disconnecting and then re-connecting the DWL-122. It's no biggie.
What I would say if you decide to spring for it is, download the latest drivers from the net, as what's provided on the CD has apparantley caused problems for a few people.
As always, YMMV, but I'm glad to report no problems at my end and it provided a much easier (not to mention cheaper) solution than trying to source a secondhand Airport card.