We had one for almost a year. Traded it for something bigger, not because of quality issues. It was the only Thor we have owned and we've owned a few over the years.
The Gemini 23TR for the most part was economical (14-16mpg) and fun to drive. We were the second owners and if there were any issues the first owner took care of them. But to our knowledge, he didn't have any. Very European styling, good fit and finish, and the Transit HD was excellent. The one issue we had concerned the terrible design of the air conditioning. It's a ducted a/c but the transition from fan to duct was very small. Very poor cooling to the front of the unit. With the down vent open, the a/c was very effective. But not in the ducted position.
Some things were kinda weird....like the sewer connection needed to be turned down to use. Not too bad if you're under 55, but kinda a pain in the butt for those of use with arthritic knees. Also the skylight was nice, but as noted, it just cooks you in Florida in the summer.
In the end, it was just a nice idea for a couple (us) who wanted to continue RVing without a big 5th Wheel or diesel pusher and didn't want to tow a car. But the small bath area and combo dinette/living room were just too small.
I've read about the horror stories with Thor, but we're not one of them. We have a good dealer and our contact with Thor was always positive.
Just our opinion.