I ride my XC bike as a commuter and all rounder when it is running 2.0 slicks and throw on the knobbies when I feel like getting dirty... it hits the curb at 23 pounds and I can keep pace with some fairly fast riders despite having some physical issues that have slowed me down a fair bit and warrants running some lower gears for climbing.

Biggest improvement is being able to get more aero on the bike and being able to spin like a gerbil on crack... most mtbs have sufficient gearing for higher speeds but suffer because they run fatter / slower tyres and are not as aerodynamic.

When I had a 1 by 8 drive... had no need for any lower gears.



Current set up... can swap to slicks and restore the rack when I need them.



I rode a century on this bike last fall before the knobbies went on... the folks I was with were amazed that a mountain bike with slicks could keep up to what was a brisk social pace.