Pros
The lifestyle is the main thing that draws people to the job. You have a lot of freedom to travel and see amazing corners of the world.
Cons
There is a high turnover rate. The pay is quite bad -- Trek Travel starts you at 12/hr and the yearly raise is on the order of 50 cents. It's insultingly low. About half the money comes from tips, but if guests don't tip then you don't get paid. Trek Travel will not pay you for tips you didn't receive. The lifestyle also can quickly become a con. You think having nothing tying you down is what you want, but that grades on you over time. It takes a year, maybe two, before you crave stability. The company also cares way, way more about profit than it does people. Guides are the face of the company but are treated quite poorly.