HUD is a no brainer.
-Nav directions inc lane guidance
-Current speed - YES
-Scroll through songs on USB audio interface - YES
-Scroll through radio stations - YES
-Scroll through phone book - I believe you can (I know at least the numbers you dialed...)
-Incoming phone call - YES
-check control messages - YES
The best part would be to have with the navigation. IMO, having turn-by turn directions on the HUD makes the best out of it.