There are GPS units available that won't even let you make any adjustments if they sense the car is in motion. The liability issue is real. That said, the ability to get into the menus while in full-screen mode would be useful, instead of having to exit that, do what you want, and then re-enable full-screen mode.

I'm still getting the "processing maps" dialog, which just stays there, and the progress meter never moves. It stayed up during a 3-hour trip today, which I had driven many times, and had the maps downloaded and in the database. I don't know what causes it, but it is a slight annoyance. I exited MM, restarted it, and the dialog went away, but came back soon.