Well, this is just my 2¢'s, but my Beige G3 MT is pretty reliable (stable) when it comes to dual-booting, and I sort of notice that Blue & White G3's (if you can get one for cheap, otherwise forget it and just get that G4...) have an aftermarket 1GHz G4 upgrade from Sonnet for somewhere between $400-$500. That, coupled with a nice speedy Maxtor/(preferred company) HD should make it sing. If you take this path, you won't have AGP but if you're a cheap-o like me, then it's the only way to go. But as for now I can only dream of such an upgrade... *stares blankly into the distance*
Some people might tell you, "Hey, the Bus Speed sucks and it doesn't have 50 PCI ports and Bwhaldahwdlahsdlkashdoiafjh" But eh, it can survive in a dual-boot world and it has legacy ports (<--- I sure hope my memory is correct on that)! Woo-whoo.
One more thing, I've read somewhere (online) that there are 1GHz G3 processors out there. As G3 = cheaper than G4, anyone know if they would work in a Beige G3? (Simple 1 line answer, please)