We've had a great experience with our Grand Design Momentum 385TH so far. There were a few issues when we first got it - nothing really relating to the construction quality. I finished installing the washer and dryer last night, and I will have a few notes for the factory on the setup in there - things that could be placed differently that would make the process of installing them easier.
We had a major storm last night, with nearly constant lightning, wind, and driving rain that lasted for quite a while. I haven't seen a storm here like that in a while, the last one with that much lightning involved a tornado.
http://www.ksl.com/?sid=35421608&nid=148&title=storm-dumps-rain-in-n-utah-temporarily-closes-i-215&s_cid=queue-2 We were sleeping in the trailer (not during the storm, too loud to sleep) and had all of the slides out, etc. It was dry as a bone inside both during and after.
Overall Grand Design does do a great job at the construction. Where they really stand out is in how they handle it when things go wrong. I'm totally satisfied.