Python works fine for me, both on my G4 and G5.
I've found P5 to be extremely stable on both of my Macs.
I've had no problems so far, and have been using it almost since P5 for MacOSX came out.

But just like P4, it definitely wants all the resources you can give it so the more RAM and processor speed, the better. I think you'll love P5, especially the material room. Just give yourself time to adjust to P5 and have fun - I know I have been. ;)

I dare you, while there is still time, to have a magnificent obsession. --William Danforth