Good to hear ... I'm not surprised, I figure a G4 at 350 mhz and 16mb graphics would be roughly equivalent to my iBook G3 at 500 mhz with 8mb graphics, and that runs Mac OSX beautifully. Chuck in another stick of RAM and you'll be amazed at the step-up in performance. As a rule of thumb, a G3 Mac is about 30% faster than the same speed PC, and a G4 is about 30% faster again. So your G4-350 would be (at a guess) equivalent to a 700mhz PC.
There are only a few tasks that would truly run slower because of the lower processor speed, such as ripping CDs to MP3, but this is no big deal.
You should be able to have a lot of fun with your PowerMac ... I am very envious of you for scoring one for free.
The question is ofcourse crazy enough to have a Mac-user laughing. What can i do?.. well i always knew that if i had something i didn't know what to do with i give it away!
So maybe you can make a 'poor' Macuser happy with this Mac and get in return a PIII 500 MHZ or so PC as a trade.