[rtpguy]

Heh, oops, didn't read the entire thread, I see it's confirmed it's a macbook4,1 - see the link I posted and buy RAM from OWC, it will take up to 6GB.
You're still running leopard, or SL? Upgrade to Snow Leopard(not Lion) if still on Leopard, and there are some performance boosts in there, then max your RAM out, I expect the machine will perform quite a bit better for you.

The Intel x3100 is crap, but unless you're doing a lot of special filters that are actually using the GPU vs CPU (maybe someone can weigh in here as I don't keep up on what PS does or doesn't use CPU vs GPU..), you won't need it for some basic editing, etc.