The GPU and video are always the Achillis Heel of any all in one system like a laptop or imac. The processor may not be the fastest but still does its job, the RAM and HD can be upgraded but the GPU is what it is. I use a Pismo Powerbook as my mian system so believe me I know how you feel. Its also why I am wary of buying the new MacBook. Used white iBooks are pretty cheap on the low end as are older Titanium Powerbooks, either would give you more elbow room on screen. Just a thought.
PB G4 15" 1.2ghz - Pismo G3 400 mhz - iBook G3 500 "Jukebox"
"SawSmurf" G4 500 - Quicksilver G4 Dual 1ghz modding...