If you want a computer for day-to-day general use, a Powerbook G4 won't cut it these days.  Internet usage really is slow, pretty much anything video-related won't work and Office 2008 is horrid on any PPC machine.  Acers have a bad name, but you could always max out the RAM cheaply and upgrade the hard disk to an SSD.  Don't trust Geekbench for PPC vs Intel tests ... Powerbook G4s were great in their time but pretty much forgotten about by the masses once Intel MBPs came out - they really did run OS X so much better.

If keen for an Intel Mac, a budget choice would be the polycarbonate Macbook, 2009 - 2010 - I've seen these go for $200 - 300 on eBay and they are still spritely to run Yosemite, and apart from brittle plastic casings are reliable solid units.  Couple this with 8GB RAM, 250GB+ SSD and it'll be a cracker.

JB