I terms of choosing a route and comparing different routes, I find the Nav in the car utter rubbish.
For example, it gives you the option for 3 different routes (as far as I can remember). But, the map is zoomed out so much when you're comparing routes that are quite similar, it's impossible to work out exactly where you'll be going.
Over 3 years in, and I'm still not 100% comfortable with the nav interface and that's coming from a bit of a geek who loves his gadgets.
Another option which I know the car has, but which I know I won't be able to find if I need it is the function which allows you to route round a road block.
On the tom tom you simply tap a couple of options and tell it that the road is blocked for the next mile (for example) and it sorts out out.
Sorry for the rant!
On the other hand, there is one function which is quite good, and one which I reckon a lot of people don't know about. You know when you're on a plane and it shows the world with your destination and a picture of the plane so you can see how far you've got to go? Well, you can do this on the Bimmer Nav too - as you get closer to your destination, the map automatically zooms in so you can always see the destination and your position on the screen, but with it still showing as much map detail as possible.
