I loaded Leopard on to the old G5 last night and have been having some fun. I backed up my Tiger system but everything seems to be running smoothly. We have it running on an Intel-based iMac at work. Having it at home makes me more appreciative of some of the new features in Mail and iCal. I don't really use those apps on the iMac.
I also built myself a little widget that loads pics of the Skylark from my Flickr RSS feed. Not perfect yet, but not too shabby for about an hour of work in Dashcode. Check it out:
Download the widget here