In general we've had very few problems with our TTs.
But miles put wear on the rig. Stuff moves when you go down the road. Make sure you have one of those square head screw drivers to tighten screws that come loose, hinges, etc.
We've had one major problem - recently a hub failed while towing. We never felt anything, only other drivers alerted us to the problem. It was caused by a broken weld where the axle attached to the mounting bracket. We had towed that trailer over 20,000 miles, but my dad was a welder. When they had the bad axles off and I could see the weld - my dad would never have allowed such a lousy job to go out his door.
Like anything mass produced - there are going to be a few that are not up to the company standards.
Over the miles we've met and talked to hundreds, maybe thousands, of RV owners. Most people are very happy with their rigs, their tow vehicle and their tires.
Yes, we almost all want something a little better, bigger, or some other different feature. If we had the money/ time/ space, etc.