We have a Thor Chateau that we bought brand new earlier this year. Spent around 25-30 nights in it this year and no problems. We had a sprinter select TT before that for a few years and it's made by keystone (Thor) and had only a couple problems that were not related to manufacturing but products (Jensen). They were corrected with the warranty. We were very happy.
We attempted to try and go the used route. The main issue we had was that every unit we went in had an unpleasant odor. Secondly, we didn't want to adopt possible other peoples problems. An rv is meant to enjoy and relax. The possibility of having problems and having to get it fixed ourselves and out of our on pocket takes away from the relaxing experience. It's much better for us that if we have an issue, that it will be taken care of and by an expert. And yes we have an ESP.