The all Mp3 demos are really amazing, they sounds really good.
But for me, all this demos have nothing to do with the arranger engine, they are all programmed under one SEQ.
You can just hear that the all parts are played in realtime, Brass, E.Piano...are not patterns, it mean a standard SEQ song.

After saw again the Video demos of NAMM: http://youtube.com/watch?v=Xy92wEdaZSo
( sounds there are recorded with a Mic Camera) but still you can hear a totally different sounds sets and arranger switch patterns bugs ( it mean a real OS status) that totally dont match with one of this new Mp3 demos.
All the nice video demos are made with a Wav player and never with a true styles, this can make the MS too and much better, try there to transpose +5/-5 semitone or BPM timescratch...
Is not a ketron fault but is only the Dream chip limitation, for your know, we have the same chipset on MS and we have ignored this all features because are really poor.

Anyway, from today is open the Musikmesse and then for sure someone can compare and make some test if really the Audya arranger sounds same like this Mp3 and when really will be released.
For sure soon someone will posting here some true news.

Enjoy what you play
cheers