The Ford E series powertrain (which is what you're talking about) is generally quite reliable. Zillions of cargo vans are used and abused in the trades with it. There are, of course, a very few oddball lemons, as with any vehicle, but generally speaking it will outlast the rest of the motorhome with only basic reasonable care and feeding.
The engine does need to rev pretty high for a truck engine to produce good power, and can be a bit noisy doing so. It also is perfectly capable of working hard for extended periods of time if needed without trouble, despite perhaps sounding like it might thrash itself to bits. If you don't let it rev, it will probably seem rather underpowered and wimpy.
