Hmm..
Bought a 23u in December, wanted the e450 chassis so it was step up for a 2017 or buy later and get a e350 (without paying premium for the chassis)
Had some minor issues, clearly rig wasn't quality checked before leaving factory. The issues were minor, solvable by me. I called Thor, they were very polite, very helpful, confirmed my repair ideas in writing (email)and scheduled me for service at a repair shop to confirm or redo as needed. Only tuff stuff was getting a shop scheduled. Not easy.
When I was shopping the rig, I initially wanted a forest river 2301 or the 2290 model with the dinnete slide. Model I looked at I could see daylight thru the upper corner of the slide extended and retracted..having had issues with my slide on the 40 ft diesel I sold, never again. From what various techs told me, the Thor box is solid, doesn't have the razzmatazz of fancier stuff but holds up.
Since I've seen ads for so many Thor class c with 100k+ including rentals, there's evidence they hold up and can take the miles; which is what I hope to do.