I installed the RC about a week ago, and I love it. Best windows OS by far. I do agree that it seems to make my system slower overall, but I'm sure that it's because all the drivers aren't fully fixed and updated yet. Once the full release comes out it should perform better. Also I need a new PC, this one is a 5 yr old P4.
If it runs well on a 5 yr old PC then that says a lot IMO. I'm pretty sick of MS's apparent need to drastically burden hardware resources more and more with each release. There's no need for that shit.
But IMO there's not much need to ever make new Windows versions anyway. XP should just be improved instead. No reason for new stuff but profit for MS. Seriously, we dont need new "features"