Wow, first let me say, it was really nice to see you post here once again.. long time no see.
in regards to Mac Os 10.3. It is "almost" fully functional (sound is not supported)... I'm running it under PearPC emulator 3.1, it's kind of slow even though I have assigned 512 meg of RAM to it. If you don't have experience with Mac then this would be best way to learn more about it. over all I would give it a 7 in scale of 1 to 10. PearPC emulator is not as sophisticated and advance as VMware there for you CPU cycle is not split properly between host and guess OS.
I would recommend it to every of with decent machine to try it.
Mac OS 10.3 was design on G4, your hardware would be good match up for G4 so I think you would be able to run it smoothly.
My system is AMD Athelon 2800+ and 1 Gig of ram 256 Meg ATI Video card.