It works fine, that's what I'm using. There's one issue they need to address which is cosmetic, not functional. If you have the RZ set to control deck 1, then switch the XP1 to use deck 3 the rekordbox software shows deck 3 as active. However, the RZ is actually controlling deck 1 rather than deck 3 so it's a little confusing. Rekordbox really needs a different "active" indication for the XP1. Obviously that only matters if you use 4 decks. Technically though it works perfectly.
Mike