I was just wondering this myself the other day, what version are you running and when did you get yours. My G4 is now about 14 months old, but I'll have to check next time I boot up what version the screen says. I didn't see any firmware updates, but here's a helpful link for drivers etc.
edit: firmware version R2.03
All installed, and ready for visitors. Infill G4 in a 2007 Saturn VUE