For me it is a tie between Litestep and Talisman. I never cared much for aston, though I haven't tried it for a while. If you can RTFM, Litestep is freeware and has a ton of 3rd party plugins, but a lot of complexity goes with that, and many's the unwary n00b that has regretted not reading the docs.
If I had to make suggestion, I would use something in the way of a shell 'enhancement', and then move on to a shell replacement if you felt it necessary. There are several apps here that will run reasonably comfortably over Explorer, and give you the feel of running without it. I'll let the hoverdesk/nextstart/desktopX crew chime in, and as I mentioned Talisman would work as well.