Played one several times... I own a Triton, and, apart from the piano (MUCH improved!), this thing still sounds like a very direct descendant...
The Karma stuff is cool, but just like most loop things, is not going to impress an arranger user with it's control differences (basically, forget about four variations and a bunch of fills, intros and endings). A whole different beast, just like the MotifXS.
I have to say, unfortunately, that except for trance and techno (and the grand piano), I am FAR more impressed with the MotifXS's. I think I'll keep my Triton, for now...
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An arranger is just a tool. What matters is what you build with it..!