My 12 y.o. son and I did this during our Lake Tahoe vacations. Everything went well till the last minutes of our time, when my son (who is very good at this, by the way) got stuck on a zip line. We called for help, and a staff member came and started towing him to the platform using a special rope. She was running fast with this rope and didn't even look in his direction. As a result, he was turned around, didn't see where he was going and slammed his legs into the hard wooden landing platform. Fortunately, he got only bruises and scratches, but this was very painful and hurt for a few days, seriously spoiling our vacation. They didn't even have an ice pack or first-aid kit. I'd really expect this kind of outfit to have a first-aid kit and basically pay more attention to safety. The edge of this platform could have soft wrapping also, for that matter, for people who are less experienced with zip lines.
If not for this accident, it would have been a five-star experience, because the ropes course is designed very well, wasn't crowded and is normally just a very fun thing to do.