The 256MB of additional RAM I bought (768MB total) a few months back was all I needed then. But now that I use VMware a fair amount I've found that I still don't have enough! I'll probably be looking to upgrade to at least a GB, probably 1.5GB.
My processor isn't that poweful either. I am suprised that my Celly 2.8 can (just about) handle running two OSes at the same time. I might consider getting a P4 (socket 478) but my computer is an emachines so it would be like putting a turbo engine into an old Morris Minor
