I've never owned a Mac personally (yet), but one of my relatives has a G4 Powerbook and I absolutely love playing around with it. Personally, I'd go for the Powerbook over the iBook, just for the more powerful G4 processors. Last I saw, most iBooks still only had G3. And if you're going to be gaming some, specifically UT, you may need the extra power.

Thread_killer is has a point though, I get the sneaky feeling that the G5's are right around the corner...like, released within the next few weeks kinda thing. Either "Call for Help" or "The ScreenSavers" over on TechTV was dropping hints to the point that made me think that. So, keep an eye out...

alph