I have a K2 Mach 2.0. It's been a great bike. It's a 2007 model that came with full Tiagra 9 speed gear. The Tiagra hardware works fine, and it was pretty much the best deal I could find on a new bike when I bought it.

The stock saddle is ridiculously heavy, but otherwise, the only thing I felt an actual need to replace was the pedals (it comes with platforms and toe clips).

Edit: Mine came with ordinary 700C wheels, though. Not 26". They were Alex something-or-others, as I recall. I still have the front, but the rear got trashed when I got rear ended by a car. The frame was fine, though.