The main benefit of the Stealth Serial Port is that it provides a "native" serial port that behaves just as if it was built-in the G4 or G3 system. With OS X, the Stealth provides that same level of compatibility - if it works with built-in serial port on a Beige G3 running Mac OS X then it will work with a Stealth.

Requirements:
OS X 10.4
Stealth Serial Port
PPC

Also available are:
Version 1.2 for OS X 10.3
Version 1.1 for OS X 10.2