I have a Midjay and in the past have owned an SD1 and also an XD3. To me as an arranger module the Midjay has two limits: the first one is the chord recognition, which is very basic (sometimes you cannot even play a simple chord inversion, because it's not recognized and so are bound to play most of times the chord with its root as the first note). The second limit is the very limited programmability of the styles.
Other than that, it's a little great sounding unit. I hope that Ketron will address these two limits in a future OS update (especially the first one, which is really annoying).