My girlfriend and I booked this trip as a day trip from Colombo.
All in all, the experience was good. The rafting was not too difficult and not too long, we crossed some rapids, the rafting and canyoning guide was funny and had great energy.
After a three hours ride in our air-conditioned car, we started our tour with rafting. They did not provide any information about equipment, so you should be smart enough, to bring a second pair of shoes or slippers, as one pair of shoes will be definitely be completely wet. We were quite disappointed of the communication with our driver and basically all guides, as the tour operator promised an English speaking guide. Well, they spoke some English words, so it's true, but good English communication is definitely something else.
Halfway of the rafting tour, we stopped and exited our boat to start canyoning. On our way to the canyon, our guide showed aus rubber-trees and some other plants, which was quite interesting. Honestly speaking, I would have expected more canyoning time and a further distance with more jumps and slides. Nonetheless, it was fun for beginners, who might be hesitating to do big jumps. There were also possibilities to avoid all jumps completely if you are too scared to jump. So that was good. At the end of the short canyoning tour, we returned to our boat and finished our journey where our driver was already waiting for us. We grabbed some food at the restaurant (where the tour ends), but the food was not specifically good nor bad. Very average.
After some bargaining with the company's boss, our private driver drove us to airport, instead of our hotel. (It was a shorter distance anyway).
To sum it up:
If you are looking for a fun activity to spice up your trip, this is the right thing to do. Probably, you can find it cheaper, but if you are tired of planning every little detail, it's nice to have everything organized for you by others. You enter the car and don't have to worry about anything. For that price tag I would expect a better level of English though. Still, we were happy about our small adventure :)