I just got my snap in and noticed the same thing and was a little dissapointed. I like the layout and control using the iphone/ipod interface when using the snap in, but the HUD only shows the current song and the next and back buttons.
I haven't tried it yet, but in idrive you can select from two different "plug in" choices, the snap in version which gives you the ipod controls and the regular version which gives you the BMW controls, I am guessing using that you still see all the songs in the playlist when scrolling on the HUD. Guess we can't have our cake and eat it too.
One thing I was suprised with is how hot my phone got, I have the media snap in with the fan (who knows if the fan really works or not), and was just playing music, the phone was almost too hot to handle when I took it out after 45 minutes of driving.