Going back to the original topic of this thread, I think that a G4 can be a _very_ usable daily-driver machine. It's all in what you expect, as several previous posters have commented.
I, personally, have a G4 cube, with 1.5gb of RAM, a 250gb IDE HDD, and a 1.5gHz 7447 G4, and a GeForce 6200 hacked video card. That machine runs 10.5 acceptably and 10.4 very well. I have no problem running Safari, on either, and I do want to try Ten-Four-Fox. Basic browsing, and terminals and X11 apps (I'm a *nix SA, by trade) all run just fine.
My mother is running a G4 MDD with 2 1.25gHz G4s and 1gb of RAM, with 10.4. She runs Microsoft Office 2004, and doesn't seem to mind the speed. The fact that 23" ACDs are cheaply available, and she has one, doesn't hurt.
So, as others have said, G4s can be plenty usable. Notice that nowhere above did I list Flash, or FaceCrap, or any other browser-beating web activity. However, I don't run Flash on my late 2010 13" MacBook Air, or my 2008 Mac Pro, either. Flash can get the Mac Pro's fans running to full speed, just because of a stupid pop-up ad. I refuse to use it.
If you do decide to go Intel Mac, Mac Minis are a very good deal. I just saw a 2010 Mac Mini go for $300+ship, last week. I bought my dad a 2009 mini for $225, back in June.
Good luck!
- Alex