I just got some WTB MotoRaptors in the race version that I had my first ride on today. They're my first pair of "real" MTB tires that didn't come stock on the bike. I was super impressed with the grip. They do naturally have a little more rolling resistance than lower tread tires. The cheaper version is only $25 new and the only complaints I really found when I researched them was weight. If you don't care about weight...

http://www.mtbr.com/cat/tires-and-wh...36_151crx.aspx