Absolutely, and aside from that, its where the majority of these bikes are MEANT to be!
After 6 years of street riding I thought I was a pretty damn good rider. Got to the track and realized I didn't know shit. I still ride 600cc's too. IMO they are already fun enough, plus I will consider moving up to 1ks whenever I feel that I am using all the performance available on a 600. Which will be never. It makes you a truly better rider. All the extra power can be a handicap for some people that makes up for their inability to turn fast.
Nothing more rewarding to me than getting passed by a 1k on the straight away at Jerez, and then passing them on the outside of the first corner to never see them again for that session.