Yes, we also use the Sundstrand C11 and C14 APU's on our fleet. Through my experience on aircraft, they seem to be a very unreliable unit, as compared to say a Garrett APU. We are seeing a lot of improvement with the C14, primarily because it is a FADEC controlled unit, but we still have uncommanded inflight shutdowns and numerous APU fails.
Now with winter coming, we get to look forward to glycol ingestion, which really isn't the APU's fault. More like an intake design problem, and a lack of knowledge of the deicing crews (who seem to like to spray glycol directly into the intake)
I am assuming you work for ConEx, and maybe your operating climate is better suited for the APU. Just a thought.
Break ground, and head into the wind. Don't break wind and head into the ground.