It could well be that the RV dealership personnel didn't want to demonstrate the TM, because they didn't know how to open/close it, and they didn't want to look unfamiliar with the product they're trying to sell, especially if this was not an authorized TM dealer. While not particularly difficult, it takes some familiarization with the setting up/taking down process. As you've no doubt determined by now, TrailManors are a bit different than popups, or other travel trailers.
We bought our 2002 2619 TM about 2 1/2 years ago, so it's about 5-6 years old now. Granted this is the first trailer we have actually owned, but not the first RV type vehicle we've used. We're not particularly rough on the TM, and I try to keep up with the 'little things' that need fixing. But in my opinion, the TM has held up well - certainly no worse than other trailers I've seen. As you mentioned, there
are going to be things that need repair - it's the just the 'nature of the beast'. The torsion bars that raise/lower the shells can go out of adjustment, but they can be re-adjusted as long as they're not damaged.
I would think, your best bet is to learn as much as you can (like you're doing here) about TrailManors to make sure it's right for you. If you happen to see someone with a TrailManor on one of your camping trips, just ask them about it. They'll no doubt be more than happy to tell you all about it!
Nick