I have a PowerBook Lombard 333Mhz with 256MB of RAM so mine is almost the same as yours.
Things to speed things up:
Shadow Killer
Use a theme without transparencies.
Get the ATI Rage Pro hack for your video card it works wonders on Quicktime acceleration - you can actually watch movies again!
It is slow - benchmarking using XBench only shows a 29/100 against a dual 800Mhz. Some networking features are faster especially if you use command line apps.