Agreed on jet boat shuttles
As a long time river guide and private boater on the Main Salmon (and other rivers) one would be hard pressed to find a better way to screw your fellow boaters than to use one of the jet boat shuttles on the Main Salmon.
In the 80's the number of jet boats encountered on the Main was limited to apx. one a day, and those were being used to bring people and goods to and from the lodges along the river. Then came jet boat shuttles (and the worst river management I know of) and the the experience of floating the Main took a dive for the worse.
You can try to rationalize how using a jet boat shuttle is o.k., but you'd just be deluding yourself. Using the Main Salmon, a National Wild & Scenic River where people come for the qualities of a wilderness float trip, as a transportation corridor when there are other options available (e.g. roads) just doesn't make sense.
(Yes, the river corridor isn't officially designated wilderness, but that doesn't change the point that most people come to the Main for wilderness qualities. And if it weren't for the damn jet boat shuttles, that's close to what they'd get.)
So please don't be part of the problem - avoid jet boat shuttles (and the commercial outfitters that use them).