I’m a huge fan of Spaces in Leopard. As a long-time Linux user I’m no stranger to the idea of virtual desktops, but I really like the way that this is implemented in OS X.
I have the bottom left corner of the screen set to trigger the Spaces overview, so any time I want to switch i can just drop the mouse pointer to the bottom corner (and the top right hot corner blanks the screen). Obviously I can use the Ctrl-[n] shortcuts to jump to a particular Space, too. I’ve settled into a pattern whereby the online stuff is generally over in the left-hand column, with iTunes top centre (those apps are set to only open on those Spaces). I have spare space over on the right for when I’m coding, running Second Life, using VMWare Fusion, or whatever.
It works well for me. I like the way I can move entire apps around by holding Ctrl and dragging applications between Spaces in the overview. Miraz Jordan has a nice series of posts on some of the other things that are possible using Spaces, too.