I know a few G5 users that feel the same way I do about Leopard. The performance hit you take running it is not worth the hassle. If you're saying it's "fine" on a G4, then my guess is that you're not noticing the hit as much or are into some of the features it offers to care. I had ALL of the updates and patches for Leopard and was starting to really hate my iMac. Didn't take me long to realize why. The OS had everything to do with that. It's super-sluggish compared to previous versions.
Same with the latest iTunes (version 9). I went back to a previous version because of it's horribly sluggish feel. Have you not noticed that? There's some major performance issues there now, especially with the iTunes store. It's as if the program was completely re-written in Flash or something. Scrolling through music was akin to bathing in molasses on my computer. lol
Not saying Leopard is completely buggered, just seems unnecessarily bloated to me. I have been told by other users that Snow Leopard did indeed address some of that bloated feel. And they're completely aware of the difference between PPC and Intel as many hardcore Mac users have multiple machines. This particular friend though noticed a speed increase on his Intel machine going from Leopard to Snow - and I believe him.
I stand by my opinion that Leopard on a single core G5 sucks and am not the only one that feels this way.
