We've owned the owned our Thor Windsport K27 for over three years, and have spent at least two years working out all sorts of problems. I am happy to say that in the past four months we've driven the RV about 1,700 miles (now have 24,000 miles), towing a twelve foot dual axel trailer with tools, motorcycle clothing, and a 900+ pound Gold Wing, and we haven't had any problems during that time...that I've noticed.
The engine AC works very well, and the roof AC keeps the coach comfortable in all situations, whether using shore power or the generator. The propane furnace heats the coach quickly and is relatively quiet.
The power of the V-10 is adequate, the mileage (normally 6.5 to 7.5 MPG) is acceptable, and the driving comfort for me is excellent, with plenty of legroom. My wife finds her captain's chair to be too large. The cat loves the big dash and the pet window next to the passenger's seat.
My biggest complaint is that the bed is much too short for me. I can't imagine why I didn't try it before buying the rig. My second biggest complaint are the reflections in the driver's side window when trying to use the mirror to back at night or in certain daytime lighting conditions.
I replaced one of the ridiculously uncomfortable dinette seats with a very comfortable pontoon boat seat, so sitting at the table for more than five minutes is possible.
The left front leveling jack is no longer leaking after having the banjo bolt remade so it will retain an o-ring to seal a persistent leak in the circuit that holds the leveler in the up position. According to Lippert, the jacks can't be rebuilt. A new one costs $500.
All batteries have been replaced with maintenance free batteries. The two coach batteries are of the deep cycle AGM type.
The above is a short list of SOME of the problems, modifications, and replacements we've had to deal with. I know that something is bound to breakdown, but until then we will enjoy the coach.
No big, not expensive, but it's ours.