Ive used TRX but not for a whole session. I mixed it in crossfit style with weights in a 30 min session and they are ok. However I personally can do similar exercises with other equipment such as swiss ball or cable machine, but they are fun and I can see the attraction. A class is always good as you learn and work to a set pace.
Its going to use your body weight - if you are very overweight you may want to think about this, it makes it more intense maybe too much. But a good trainer adapts for beginners - can you speak to the trainer or coach and ask them first? I recommend tho a kettelbell or body combat to complement this. It might be a better place to start as well...