Colorado/Canyons are only available with the ext cab or crew cab no reg cab is offered. On the Colorado forum people are getting 18 MPG or so in city driving and 22-24 highway with the V6. I'm really curious about the 4cyl Duramax diesel coming out later this year, some are guessing/hoping for over 30 MPG highway with it.
Here is the video of TFL Truck towing around 5500 lbs up to Eisenhower Tunnel on I-70 in CO. It didn't do too bad if you don't mind the high RPMs.
Canyon up the Ike Gauntlet