This was my first time zip lining and I rode the lower line. I was really scared before we started and almost backed out, but once we got going it was a lot of fun. I'm thinking I'll try the upper line the next time I'm in Vegas.
As a side note, there was a woman in line ahead of me with a boy who appeared about 9 years old and he was terrified and crying. It seemed like his mom was going to make him go anyway. I said something to an employee and he did not let the boy go on and had then walk back down. I really appreciated him doing that because it really would have bothered me to see a child be forced to do that.