My boyfriend and I did the mid morning rafting down River Ayung. Booking process was easy, I booked online the day before and we were picked up from our villa with no problems. I chose Sobek as it had been recommended by some of the locals and from my understanding it is Balinese owned which swung me in an attempt at sustainable tourism (avoiding the Australian owned companies).
The company seemed very professional, we felt safe (I can't swim!), I can't remember the name of our guide but he was great, all the staff were full of energy and making us laugh. The white water rafting was a great way to see the jungle, we had a great time I wanted to do it again instantly!
The experience also came with a buffet lunch, which was a nice added extra, however I wasn't too keen on what was available. Didn't detract from the day at all as was there for the white water rafting!