Although the two aren't synced on Rolands, yet (I've got a request in), it seems very possible to combine arranger play AND SMFs on newer Rolands (and Yamaha's, I think - maybe others).

I've got a post here describing how it can be done (on a Roland, at least);
http://tinyurl.com/yqhly6

I was just wondering if anyone uses this method much, and any feedback about potential problems, or features I haven't thought of...?

The Yamaha does this very easily. I often play a midiFILE, and turn an arranger drum pattern on, or add the multipad drums to it. Works like a charm! The SMF drums disapear, and you now have realtime control over fill ins and rhythm style changes.

The Midjay does it very well. I don't ever use it because I seldom use midi files, but I often use the sound effects along with styles.
DonM

Thats the beauty of the multi-functional MidJay...you can play all modes at the SAME time with individual slider controls
SMF,MP3,STY,SFX, Voc/Harm & Lyrics too all in a 7lb box! If they just made the display bigger on future models.

The Rolands can't do both at the same time, nor replace the SMFs drumtrack with an arranger one (great feature), but primarily, I was interested in going seamlessly from SMF to arranger and back to give me a quasi-chord sequencer ability, since Roland dropped my favorite arranger feature.

Are any of you using it in this way? The ability of the Roland to combine both modes with the SMF Marker function makes back and forth very easy.