I would like to point to one thing... Windows 7 feels like faster but it is not ... based on many benchmarks I did, It performed almost same as vista... the difference is that the GUI is faster. I thought at the beginning It was something wrong with my pc but then I found also an article talking about the same thing :
http://www.nillabyte.com/blog.php?b=128
Utorrent working fine here 200KB/sec downloads .. If you are still having problems try this
Options > Preference > Advanced > Disk Cache
and remove checkmark next to the Enable caching of disk writes...
However, I still prefer XP, just MHO.