There are 6 assignable buttons on the dash right under the CD slot. They do not have to be audio presets.

The air-recirc button on the steering wheel is actually just a placeholder for vehicles not equipped with Lane Departure Warning. So for people who order that option, that button is more useful, turning the system on/off.

BMW has unfortunately gotten away from engineering buttons with a more tactile feel. On my old X3, everything from all steering wheel buttons, to the foglamp switch, to even the heated seat buttons, had a nice detent or "click" (not necessarily audible) to it.