From what i heard, it can be a bit cranky with processor heavy programs like Wing3D, music maker programs, and even some of those ''cure cancer while your computer is inactive'' programs, i think their called @home, or something like that.
Another thing, most pc's running vista now, should easily be able to use it, my dad has it installed and found it to be more stable than both XP and Vista, and even though he is an anti-windows man, he seriously considered to install it on all the other pc's at home as well, as a secondary OS.
Though, if your in need of drivers, expect many Blue Screen Of Death moments, my dad had to wait 2 days for a stable driver for his video card came out, otherwise, the pc would BSOD every 20 or so minutes.
http://hardwaremania.com/news/wp-conten ... sod_01.jpg
Though they made the BSOD's a bit more understandable to read with a online library, and i think their summarized in a help topic as well, what happens if you don't have internet, not that i think anyone owning Win 7 doesn't have internet, but think about it, thats a serious fault on Microshits side.
EDIT: no, not illegally downloading it and installing it on the other pc's, or atleast, not that i know of.