The last (only) article I read about it said you basically need a new computer or ram upgrade to run it unless you have a huge amount already. I forgot the amount but I recall I don't have near enough and I have 4 gigs. So, that's really shit to need more than that for an OS. I'll eventually upgrade I'm sure but not on this PC.
Edit: I read some quote on a linked article and MS is now saying you won't need to upgrade so I guess they changed some things around. Nevermind the above I suppose.