My SD7 has been stable. I had an Audya for several years and it never locked up. I'm not one to experiment too much with converted styles, as there are tons of Ketron styles available.
My main issue with SD7, in addition to the text and fingering omissions, is the length and weight. It is manageable, but I'm having problems with the old body. Have to be really careful with my back and knee. I'm finding the Korg easier to deal with when moving, setting up, etc.
I have considered Midjay Pro, but not sure I want to go the module route again either.
The SD7 sure sounds great.