I've been doing this for a few months now and everything is fine and dandy.
Your PowerBook should be able to detect it automatically through Rendezvous, since that's how the base station shares it. Just launch Print Center and "Add Printer".
For the PC:
Install printer drivers first
1) "Add Printer"
2) "Local Printer" (don't automatically detect)
3) "Create new port" - "Standard TCP/IP Port". This will take you to some new wizard.
4) Enter Printer IP address and port name:
- IP address is that of your base station (check either from "Network" System Preferences Tab or "AirPort Admin" app. Usually 10.0.1.1)
- Port is 9100
- You should get something like IP_10.0.1.1:9100
I stepped this through on my Windows 2000 system, but I don't imagine Windows has evolved much...
Hmm... just compare the number of steps involved.
edit: added Windows instructions