Lumia 920 Concerns
I have noticed the same thing with my Red Nokia Lumia 920. I have only used music via Xbox Music under my Xbox Music Pass. It will display the initial artist and song that you have up, but when you manually change songs or go to another selection off the iDrive and then go back to the multimedia, the title is not updated.
I have not yet tried it when downloading music onto my phone. Have you done this already? If so, does it still not update the display information even after you played only downloaded content on your phone?
When I was in Germany, I had a WP7.5 and when I paired it with the BMW loaner that Pentagon Car Sales let me drive, I was having the same issues as well when playing music via my Zune Music Pass. I don't recall it not updating when I played downloaded content from the phone's storage itself. I could be wrong though.
Do you know if the Lumia 920 will eventually receive more capabilities in the future rather than the "voice" and "music" features that we're limited to in the meantime? Messages, calendar, and tasks would be great to see in the display, but the Lumia 920 has yet to have those features.
As far as the music goes, I think you're good to go though with everything that the F10 offers: the ability to add music to the internal 12GB hard drive in the car, a USB plug for external music, bluetooth from your phone, SIRIUS Radio, and a CD player. If you have all of that combined while you're on the road available to you at an iDrive length away, I think that's pretty sick. You're a driver and a DJ at the same time. Amazing. Let me know if you hear anything else on the Lumia 920