I had a few issues with my M2, which was a 2007 factory build. I was not at all impressed with the build quality. As an example, during routine maintenance and inspection (20k) I noticed that one of the tranny oil cooler lines was rubbed nearly all of the way thru by the transmission mount. In fact, all of the wiring and air line routing was a haphazard mess IMHO (that kind of stuff drives me nuts). Also, the "chassis module" ECU is mounted in a place that gets spray and muck off of the driveshaft.
Another issue on the models with air brakes is that the rear brake actuators hang down and are very vulnerable to damage when off the pavement.
As a positive, the M2 does have great visibility and turning radius though.
If you are looking for an intermediate truck to build on, and plan on traveling south of the border, I would strongly recommend that you stay away from the newer rigs with DPF. (diesel particulate filter) They are not intended to run on anything except ultra low sulfur diesel and are prone to problems no matter what they are fed.
hope this helps, YMMV, JMHO, etc..........