Works fine here (Win7 RC 64-bit - Keyclone 1.9i - 5x WoW folders all symlinked). I'll be changing for Win7 RTM 64-bit (MSDN subscription FTW!) later this week.

I generally sit at about 40% CPU utililization across all 4 cores on my Q6600 (OC'd a bit). I have had a few issues when 1 of the wow windows crashes or DCs - no more than I've seen on XP or Vista though. I haven't had any issues with keyclone though. If anything, my CPU utililization only goes down, as it should, when one of the 5 windows crashes.

I wouldn't make assumtions about the cause of your problems until it's been worked through.