My experience: I have been using a Farallon (now Orinoco) PC slot card about 2.5 years with zero problems. Works great. Clearly quite happy with it. But, I am running 9.2.2 on my Lombard and I don't believe Orinoco makes a card that runs OS X. So if you want OS X and 802.11g capability, other sources will probably be best.
Harv