My wife and I did this in 2014, so maybe things may have changed, but our raft guide (along with most others) really tried to pressure us into buying their crafts. There were also people along the river throwing things at the rafts as we passed buy to try to get us to purchase. It felt very pressured and awkward. Also, when stopped at the church, the locals were pretty aggressive.
At the time, no one had mentioned to us about the crafts or aggressiveness of the locals and it left a bad taste in our mouths, which wouldn't have been the case had we known ahead of time. In the end, we still really enjoyed the excursion.