Fellow Linnstrument owner here. Agree completely on your point about the diversity of chords. It's really really hard to imagine going back to a piano layout and attempting to get back to the high water mark of where I'm at with a Linnstrument today. If something could be described as a gateway drug to harmony and music theory in general, this would be it.

For people who haven't used one of these, a 2D isomorphic layout (as seen in the Linnstrument and others) enables you to see chords, scales and progressions initially as 2D glyphs, and later as a lattice structure as your eyes/hands become more accustomed to the layout. Learn the pattern for a given scale or chord once and you can relocate it anywhere with almost no mental cost, so transposition is effortless compared to a piano.

I agree with the other poster in this thread on the "four corner" problem, which comes up surprisingly often. I think Roger Linn has spent a lot of time making a big deal about the Linnstrument's sliding and MPE capabilities, but the isomorphic layout is really the workhorse.

If any iPad owners are looking to try out an isomorphic layout and don't want to shell out for a Linnstrument, check out Musix Pro.