Don't do it, unless....
If you have OS 9 on yours, and concerned about speed, you might want to keep your system! I have a the 400 Mhz G3 PowerBook and can relate to your problem.
Everything runs mightly slow when you have a bunch of apps open (two or three). I like to have Entourage, Safari and iTunes running at the same, with eDonkey (filesharing app) running in the "background". (Don't worry about that too much if you don't know what I'm talking about.)
But back to the point, if you run Photoshop, or any other app that likes to crash in OS 9 for that matter, you may reap benefits from upgrading to X.2, with virtually no crashes (I have them only when I try to connect to a Windows machine sometimes).
The lost time in speed more than surely makes up for the gained time in productivity while you would be wasting that time watching the OS 9 machine reboot, run DiskFirstAid, etc.
One other note and I'll end this:
GoLive is PAINFULLY SLOW on this machine! If you just e-mail and browse the net, stay with what you've got.