I tried DesktopX, and it just seemed like a waste of system resources, for only changing the appearance of XP. Fonts didn't always look that great...pop up boxes weren't always readable. In the end, it just wasn't worth adding anything on to the shell like that.
I tried aston a while back and I hated it. It just felt like the only reason they made it look and feel different was to make it look and feel different, and not necessarily to make a better shell. It just seemed way overblown and very inefficient for what it was. I certainly wouldn't ever spend any money on it. Litestep is pretty decent. Check out http://www.shellfront.org for lots of great information. Though nothing beats kde 3.4.1 with translucency and shading.