I had an opportunity to load Leopard on a 1.2 Ghz G4 laptop & use it for a day or so - did not find any issues. It was very nice, smooth, and well laid out. Unfortunately I don't have any Macs new enough to run it - It requires 512 MB RAM and over 867+ Mhz CPU. My Dual G4/450 with 1G RAM won't install it. :( There is a streaming/downloadable demo video/walkthrough on Apple's web site. It's easy to find presently.
The sad thing is the lady I loaded it for knows almost nothing about Macs or even computers. She doesn't even comprehend what she really has!!! Grumf. At least it will be easier to learn than WindoZzze... ;)