In case you are thinking of signing up, here's my two bits worth. I've rafted most of the rivers in California over the years (sadly, no Cherry Creek) and spent 10 days on an oar boat on the Colorado a decade ago. At first I was disappointed we weren't paddling, but I was amazed at how much fun we had just hanging on. The amount of water in the big rapids has to be felt to be appreciated. Lava Falls lived up to its reputation. The Colorado is the perfect river for Cobra drivers!
Rich