My main laptop is a Thinkpad from 2006 and it has no problems running Gnome shell. You can also find plenty of videos online where people show off unity running

My main laptop is a Thinkpad from 2006 and it has no problems running Gnome shell. You can also find plenty of videos online where people show off unity running on Nexus 7. It's a combination of the requirements being quite low and the hardware in question actually being quite powerful. If you can't find support for animated desktops in Unity, then it's probably because none of the people who actually write the code thought it was a valuable addition.