Love it! I had three of these (can't remember if G4 or G5 - I think G4) at the digital photo lab I ran from 1998-2010. I ended up buying the second one because the first one would randomly freeze. Took two trips to Apple to find a fault in the CDROM drive which caused some errors in the OS installation. Was frustrating as hell! Once that was solved, it and the other three ran for years without much hiccup. Agree that the rack mount installation was a PITA.
I also had the XServe RAID fully loaded. I don't even remember what that sucker cost but it was a LOT. Also ran for years and years. Used it for my photo business after I sold down the lab.