Had one in the previous RV. It worked great. It was quiet as long as you were not in the bedroom, but if you used it at night, or used the electric heat pump at night you found you were sleeping right on top of the noise. Again, because it is in the back it is much quieter during daytime activities up front.
I was told that it is no longer used because Coleman no longer supported the product. If this is true it will make future repair problematic. When I had that fear in the past, as my A/C did need service and a part, I was assured by the technician (who I know well) that worst case scenario I could easily put two A/C units on the roof and pull the basement air without "significant" cost.
We had that coach for 11 years, traveling all through the hot West. The basement A/C worked well.