If enough of the fans complain about the auto difficulty system, there's a strong chance they'll patch it to make it optional. Or at least they will if they want to keep their customers all happy. It's probably too late for them to change it for launch.
Suggest you can do this over at their FB site as they have Q&A sessions with fans/potential buyers and seem to be receptive to comments/suggestions:
I;m really looking forward to this game, but I have a wii... Any news on when that PC version is being released?
Even in that video, they're being as misleading as they can get away with by implying Guitar Hero is their main/only competitor and then downplaying Rock Band by saying you don't need a "MIDI connector or anything like that" to play Rocksmith.
I didn't realize there's gonna be a PC version until just now. Any speculation as to whether it would be less lag prone on PC due to better processing hardware? Since it's a single player game, having a huge screen isn't as necessary.