Here's a somewhat dated link that may help. http://www.insanely-great.com/features/020215.html It doesn't address the newer iBook models, but I think it'll give you an idea of what the pros and cons are. Keep in mind too that the video cards in the newer iBooks support Quartz Extreme and there's a hack that lets you span displays on some models. There's been quite a few incarnations of the iBook and you don't say which one you're considering, but one of the only departments that a new iBook doesn't trash a pismo in is expandability. iBooks are faster (and has an improved firewire port) They are lighter and smaller The screens are better They are more durable Inexpensive DVD/CDRW option Also be aware that buying a used laptop is more risky than buying a used desktop. Laptops get bounced around a lot more and even if well taken care of their batteries deteriorate over time. I have a 600 mhz ibook with a 100 mhz bus. It's faster than a stock 450 mhz cube for most things. It's probably the best computer purchase I've ever made. Like I said, if expandability is important, get the pismo. I wouldn't worry about upgradeability too much. It's usually cheaper to sell the existing computer and get a newer model than to do significant upgrades to an existing one. The only computer I'll spend much money on upgrades for is the cube, -and only because it's so unique. If you really want a G4 in a laptop for cheap, why not just get a used TiBook?