One thing that is completely different between XS and arranger operation is the fills...

On an arranger, the second you push the 'fill' buttons, it drops into the fill. On the XS, you have to push the button for the fill one bar before you need it. You can't just use the tail end of the fill (AFAIK), you always have to play the entire fill.

For those of us very used to arrangers, this is a VERY difficult thing to get used to...