I've heard that those cards based on NEC chipsets have the best performance and compatibility under OS X. I'm using an Adaptec AUA-1420A, (NEC-based) and have had no problems with it. It even has a nifty plug for a power adapter for supplying juice to devices requiring in excess of 500mA (such as bus-powered 2.5" hard drives, etc).

I use it in every PowerBook (from 2400c to original G4) that requires either USB 2.0 speeds, or USB capabilities period. It even works under OS 9.