I will have to agree with Scooterman! I sold my 2001 YZF 600R to my brother the day I bought my 2001 R6. During normal rides, he is able to keep up with me just fine. The are VERY comfortable bikes and can be ridden all day without any discomfort.
The thing I like most about the 600R is their reliabilty!! My brother, nor I, have ever had any problems with the bike. The only thing that I don't like is the weight. But, that's just me. I guess you could say the added weight is a good thing. Maybe that is what makes the bike feel so stable.
So, go ahead and buy the bike. They are very fun, and you can't go wrong!!