Well it has been a week or so since the Leopard arrived on the G5 * 2GHz * 4GB and I have to say it's sweet. The new finder view coverflow with quick look is great for photo and file review. The dock tweaks look good and replace folders with useful links that previously littered the desktop.
The only issues I have seen are video extraction application "TivoTool" not working, a rather worrying Crash while sleeping and application windows sticking to the glass in Spaces.
Spaces does work with two monitors ( different sizes ) just as I hoped it would. Fantastic.