Not much...

but when playing left hand bass its good to play on top of a midi file,...
markers an loops are a nice thing when using midifiles..
But most of the time, i am just using the style drums track when piano playing

On the korg pa4x, midi file are also used to create (stylesparts)
Where the results of the style creator (converting midi file to style) in general are acceptable (with some edditing)
I tend to create the iconic parts like bass and guitar patterns to a standard style to get sometimes stunning results..

In the end, i prefer styles..
Why?
Probably because i allways did..

looking forward to multi track audio files on the only brand that supports these...