My wife and I recently spent a half-day at Saxeten Canyon with Alpin Raft. The canyoning it self was wonderful - anyone who likes extreme sports, climbing, jumping, etc should find it to be fun and different than other sports that they have done before. For those who are a bit hesitant, I will be honest and say that, for me, it was frightening at times. Jumping from a 4 metre/12 foot rock into a splash pool below nearly had me in tears since it's a lot higher when you're actually up there!
That said, our guides were incredibly patient, kind and good-humoured. They allowed each of us (there were 4 in our group) to take our time and to be comfortable (or at least ready) for each jump/slide/decent and, in the end, that made us feel safe, secure and confident to move forward.
I would recommend Alpin Raft to anyone who is interested in extreme sports while in Interlaken. They are professional and take safety seriously but aren't too serious - they struck a great balance between ensuring our safety/security and making us feel like true adventurers!