I'm trying to decide between a refurbished (lease return) Powerbook 1.5 Ghz for $700 and a new entry-level MacBook. The advantages of the PowerBook are that I prefer the larger 15-inch screen, and I save a few hundred dollars. How superior is the MacBook SR in terms of processing power compared to the PowerBook? Will the MacBook last me a lot longer? (I think the PowerBook is 2-3 years old.) I'm not doing any heavy-duty stuff (word processing, web surfing, some math programs), but I'd like a big speed improvement over my current 400 Mhz Powerbook!!! Thanks.