The chassis, being gas or diesel, shouldn't be a problem considering Thor does not build them. From the problem postings I have read written by owners of new rigs I wouldn't buy new but then that applies to just about any coach builder as far as I'm concerned. We're headed into our forth year of ownership of an eight year old Thor product and are very satisfied with the coach. The house side is holding up very well while the Ford chassis is rock solid.
Opinions are like backsides. Everyone has one and they all stink but your own.