I have the Thunder Tiger trainer also, but it's the older one. My only gripe is that the whole top is plastic, so if I have a moderately damaging crash (which I did on the first flight due to a battery that didn't stay put) you can't just break out the balsa and covering iron and cobble it back together. The wind tosses it around a lot, so I don't like to instruct with it on windy days. Some of the other instructors who use Avistars keep flying with their students though, and they do fine.

As for brands to stay away from, MDS comes to mind as having a really bad reputation, and Super Tigres take a long time to break in and can be frustrating to tune. ST's are quality engines, but the design is more geared toward durability and performance instead of being user friendly. The first generation of Evolutions had a few bad apples, including one that I still have in my garage that cannot be tuned to run reliably in any possible way. For stuff that's currently manufactured though with reliability and ease of break in and tuning the top priorities, I'd say OS, Evolution, and Thunder Tiger are all top tier, with Magnum/ASP (they are the same) and the MECOA line as second tier but still serviceable, and everything else either is inferior quality or has design choices that make them poor beginner choices.