I regularily ride my mtn bike on the road and don't own a road bike. I commute to the store, work, wherever I have to go. I have two wheelsets, one with slicks, one with knobs. I'll do an eight hour ride on the road with thinking twice. If someone gave me a nice road bike, I'd certainly take it but have no plans to buy one.

I think my longest ride with knobs was ~175 miles in one day. I went in a semi-circular route and ended up at a friends house and rode 60 miles home the next morning. I was extremely fit and strong, but it was a long day and have to say that the knobs do slow you down some.

Penguin