Here's the basic scoop: RB3, is actually good at teaching how to play exotic alternate keyboards like the jammer. I estimate it is 2-300% better at teaching some key musical skills (with some caveats), than the several other kinds of practice I've tried.
It's not perfect (duh - it was never designed for this), but it was well enough designed for teaching intrumental skills that it generalizes to a crazy instrument like the jammer. What's more, it's simulation of being in a "real" rock band is fun and engaging.
I'm been busy and having a good time at various things, and spare moments are spent with RB3, so blogging has been negected. However I have collected a fair bit of notes, and hope to make clear where RB3 is useful.