I bought a 15" PowerBook that was refurbished (800 MHz, $1700). Runs great and has a full warranty through AppleCare. Highly recommended.
I'm not sure that $2000 for a G5 is enough to make you run for the hills. You'll spend at least $1500 for a good PC system and then you'll ruin it with a copy of Windows.
I am considering the switch to Mac full-time - I'm tired of the security issues and Microsoft's direction with Windows.
Would I pay $2700 for a new PowerBook? Now that I've seen the light, absolutely. Everything works flawlessly with mine and that peace of mind is worth it to me.