I did the 12 mile Colorado River kayak tour from the Hoover Dam. It was absolutely incredible. The whole journey was beautiful and exhilarating. Our guide was fun, funny, and very knowledgeable. He was good at gauging the abilities of the group and keeping us moving at a good pace. Pick up/drop off and the ride were pleasant and comfortable. Safety was always emphasized and the trip was thrilling but never dangerous.
It was interesting to compare this excursion with the Grand Canyon tour I took with another company the day before. The quality difference was huge. Evolution Expeditions went right at every place the other company went wrong. (Even the boxed lunch was tastier, healthier, and better quality!) I'd love to do another trip with them!