We have a 2005 Damon Astoria 38.6' DP (Thor bought Damon in 2003) that we have had since January 09' and absolutely love it. I pull a 20' car hauler behind it with no problems. It's been a dream to drive and use. We've had issues that seem normal to what I read about other brands including the high end ones. Just address the issue & fix it when it happens to keep the rig in good shape.
I would certainly not hesitate to purchase a Thor product if it met our needs and was at the right price. With that, we plan to keep this one until the wheels fall off or I physically can't drive anymore. :).