Fresh off the assembly line Thor products appear to run hot or cold. Minor issues quickly resolved while others could be best described as in for service more than on the road. Haven't read much with problems concerning Challengers. A bit more with Hurricanes and Ace models but Thor does produce a lot of both. You also have to consider what one owner might consider a minor problem another is ready to dump the coach.
In my camping group we have two Thor Hurricanes (one new and one older) and one Challenger (older). I have one of the older Hurricanes. Overall we are all happy with our rigs but I wouldn't call any of the rigs 100% problem free but nothing that has left any of any of us on the side of the road, ending an outing early or had the rigs in the shop for weeks on end.
The Challengers are Thor's higher end gas models. A bit better materials used for the interior and such then the Hurricane or Ace which should make for a bit more comfort while on the road more than a weekend or summer vacations. For our next coach we're looking at diesel platforms but should I change my mind and go with gasoline I would have no problems going with a Challenger.