First, I think it's too dark for in car use. It should have white background. Yes, I know it's hard to look cool with a white background, but that's where the challenge should be! Of course, for night time it could be dimmed, or even inversed, but for in car use the priority should be daylight viewability.
Maybe it's not clear to me from your pictures, but it does look too static to me. I think it reflects most front ends/skins designed in the past (CF, DFX, others). I think we should look at a "blank" customizable background with dynamically added information as needed.
A bit like MeeGo does - which look a lot like Carwings dynamic, which in turn is based on the Infiniti/Nissan NAV computer, it starts with just two buttons, menu and tools I believe. Garmin MobilePC is like this too, the start screen has only two big giant buttons, where to? and menu or whatever.
So I mean IF and ONLY WHEN music starts playing is that the song information labels and transport buttons (play/pause/ff/rwd) should appear. Otherwise, no useless play button, that's just a waste of space and a distraction. You could be listening to the OEM radio instead. NEVER assume the iPad will be playing music at all times.
When music starts playing, then you click on the song title and then more and more info progressively may load and fill the blank space. Album, year, artist, wikipedia bio links, lyrics, more of the same artist, create a pandora station with this song, etc. It would be cool to perhaps relay info to the mp3car server (optional) and display an option to listen to what people from this community are listening (provided you're able to, etc.). Just ideas.
Same thing with gauges. You could display OBD info on top of the song information, or vice versa. Depends on where you last clicked, depending on how much screen real state you have left (so if lyrics are open, you open the info on top of it, but not if there's enough space, etc.). No new page loading/drawing necessary.
It would be cool to have a button to search the library with a big on screen keyboard, for when voice search does not work, or when you have a passenger to manage it.
I may design something on PS to show how it would work, but you can check a video I made for my CF skin (Minimalist flat, in progress). I had the same objectives as above, but CF skin language is too limited to get where I wanted to:
Note the song information that can be expanded, and the main menu functions that are available from ANY screen. That's about it though.
Just my 2c.