I'd like to see a single menu structure: At the moment, there is typically a menu button in the bottom left, and another menu button in the bottom right - it would be nice if they could be all in together.
Secondly - I'd echo my request for there to be a single row of buttons on the bottom of the screen - so the Destinator buttons are on the same row as say the volume buttons.
Thirdly - the blue/purple bar that appears across the bottom of MM/D3 - the one that has the satellite signal strength at the right hand end - can that bar be supressed, and the signal strength meter be shown as a small graphic overlay in one of the corners? It's so small so as to be practically useless where it is.
Four: The compass rose in the top right is hopeless at it's current size when you're driving the car (I configure for my direction being straight up, rather than north being straight up). Maybe a changed graphic to indicate north (a bigger single arrow for example).
Finally, can it be set up so that the buttons that appear at the bottom of the screen for Destinator are user configurable? For example, I never use the Q/S button, so I'd like to be able to hide it.
I figure that most of this can be done by clever skinning, but I'm still not all that savvy with building skins :-(
That's all I can think of off the top of my head :-)