I loaded BCN on my friends nexus 7 and its great! The higher screen resolution means it shows more map then a phones screen at a given view level. The only thing I have seen with it is the nexus screen is not that bright compared to most phones. The nexus looks ideal for off-road nav, but the screen brightness is a concern for me. A little research shows its as good or better in raw brightness then any other 7" tablet. To get a bright screen you have to move up to the 10.1" (too big) tablets and to much higher price ranges.
My phones screen is roughly twice the brightness of the nexus 7...bums me out but I dont want a giant 10.1 cluttering up the truck.