We are on our third (and probably last RV), without any significant problems. Bought all three used: 2006 A Liner, 2008 Pioneer Sprit 22' TT and our 24' Nexus Class C. On the first two the "PDI" was completely on me as we bought from private parties. Both were in "As New" condition with little mileage and we enjoyed 5 years of trouble free use.
Bought the Nexus used(6,205 miles), from La Mesa RV so there was the formal dealer PDI and it went very well. After 20,000 miles in just over a year we are still happy campers. Our cross country trip took us through Elkhart (no accident), and I had the factory add two minor mods (spare tire under coach mount and another set of seat belts), as well as addressing two repairs.
The fuel fill obstruction was corrected no charge (3 hours of labor), despite being 1.5 years out of warranty and not the original owner. The damage incurred after a couple of thousand potholes back east which resulted in several machine screws shearing off was repaired in three hours (at $75 p/hr), and I was charged for just two.
I don't think our experience has been particularly unique. The key to our success was to seek out lightly used, well maintained late model quality RV's. The bonus is the huge amount of money we saved on each upgrade. Actively using and maintaining them contributes to the overall positive experience as well.
There is a lot of junk out there both new and used and the best way is to simply avoid the low end garbage, thoroughly inspect and then just use and enjoy. :C