I have a 2001 X 600, and I just had it on the lake this weekend, with my girlfriend on the back, and got 105mph. And I have one tooth smaller gear in the chaincase, so my stock topend should be higher.... and higher yet if I ditch the girlfriend!
I dont notice any brake noise, though. The only time I hear any noise from the brakes is when I am squeezing on them.
Also, doboy, my sled has the same idle characteristics. I'm not too worried about it, I have heard the same thing from alot of other 600X riders.