One of the major reasons for using my B&W G3 is for backups. I have a 2TB RAID enclosure attached and my G3 receives backups from a 17" MBP, a 17" PB, a Mac Pro, a 2.3 Dual Core G5, a 2.7Ghz Dual Processor G5, a 12" PowerBook and a 15" MBP.
I use Carbon Copy Cloner in all cases to create sparsebundles (which Tiger on the G3 understands). CCC lets you set a time schedule for your backups and you can make as many backups as you desire for whatever you want to backup to wherever you want to backup (including network drives). CCC allows you to 'fail silently' if the target drive is not present when the backup goes off and it will prompt you for backup (or skip) if a backup is missed.
My MP also backs up (using CCC) it's media drive to my G4 that has two 3TB internal drives.
Since I use sparsebundles, the data is compressed and the app sees a 'drive' large enough to accommodate the backup. Collectively, it all fits on a 2TB RAID. Since these are disk images then, I can transfer them to any media to facilitate a recovery. Further, I have 3TB in Dropbox so periodically I will push these up to Dropbox so that I can access them anywhere should I need to.
My only issue is that since Tiger (the G3 uses Tiger Server) does not understand sparse disk images (although sparse bundles are DMGs) I cannot use them. I've had problems moving those around in the past because Tiger sees them as folders and not DMGs.
I was using Time Machine for years, but the variety of OS that I use was causing complications, many of which were causing the G3 to lock up during a backup. So, CCC became the solution. CCC will also automatically mount the network drive/share/DMG you specify and then eject it when done. Another reason I use it.
Finally, when logged in, CCC also backs up the server to the RAID so there's a sparsebundle DMG of the server too.
So far it's worked out pretty well.