I have NAV in my X5, but know a little-known trick from other BMW's "business" radios. Many of the standard BMW radios have an "M" button. Who knows what the "M" really stands for, but I always thought of it as "manual."

If you push the "M" button when in radio mode, you can change the radio channel by 0.1 increments either up or down with the arrow keys.

Also, if in CD mode, the "M" button will allow you to either fast-forward or reverse through a song with the arrow keys. It comes in handy sometimes!!