I purchased a coach with this engine new in 2012 so can speak from experience. You are going to hear plenty of negative information. Most who comment have no personal experience. The engine that does have a "deserved" bad reputation is the Maxxforce 13 and was not used in motorhomes. Plenty of documented problems with this motor. It was a large truck engine. The Maxxforce 10 was a smaller engine and used in school busses, smaller trucks and motorhomes. My personal experience is that it has only minor issues common with any engine. This engine does not use DEF fluid like most engines of this age. It does not like to be idled for long periods. Idling for extended periods will cause problems. It also likes to be driven "hard" and does great on the interstate. I have found power/torque to be adequate and pull a jeep wrangler in the mountain areas. It also has an exhaust brake so make sure this is working properly. It is fairly easy to maintain and have been able to complete most routine jobs (oil/filter changes) myself. There are two fuel filters, one of which is located on top of the engine that need to be changed. There has been at least one computer update so make sure this has been completed when you check the maintenance records.
I suspect many negative comments will follow this post. Many will give very short responses like "run away" but provide no details or personal experience. Others will probably comment about decreased resale value etc. but if you are purchasing you may try and use this to your advantage. Personally I would not hesitate to purchase another motor home with this engine but will be surprised if the negative comments don't start showing up shortly.
Robert and Marisa
2012 Monaco Knight 40 DFT
2012 Jeep Rubicon