After 30 days...oyur computer will self-destruct....really....NOT. Not sure, but worst case, you won't be able to use the application (program). In any case, you should know weel befroe then if it's something you would like to keep (and pay for), so odds are you won't know what would happen after 30 days. I ran it for 1 day before I paid.
Aston, which I use now, is a lightweight shell replacement for windows. That just means it replaces the standard windows shell (explorer, etc) look and feel.
I tried hoverdesk for a while...it's very similar to Nextstart (from what I remember)
ODnet comes with many great apps (Windowblinds, Objectbar, WebBlinds, etc) that allow you to customize many aspects of your computer.
Once again, try them all and decide for yourself.
Hope this helps