I did a GAP Adventure to Ecuador (Inland and Amazon) and for $900 for 16 days, my partner and I felt we got a great deal. Our guide Henry was a local but works for several tour companies as a freelance guide. He was well educated, spoke English well, and took good care of our group. He handled the logistics of getting us around and made sure we knew all of the options for things to do with our time at each stop. For my first introduction to travel in South America, I thought the trip was excellent. Having some time both before and after the GAP tour to explore Quito and then Bogota Colombia was a great thing to do as well.
I'll be looking at GAP again for further exploration of South America in the future.