It is a great feature.
think about it-all those poorly written (esply those that are free on the net)drum tracks of SMF songs will be replaced by arranger's styles(and fills and variations) in real time.
Meaning your rock style drums(on SMF) can become a latin style/fills /variations with latin kit in realtime or can be a funk style with another button.I think it's a major feature.why can't others follow that route yet?