Still trying to figure out where I can tap to get a reverse gear signal on my car. 

If I don't connect the reverse gear signal wire, will the navigation system still work fine?

i dont have mine hooked up and it works just fine. you're prob gonna have to run a wire from the back of the reverse light. if you have a back up camera you are going to need that wire hooked up if you want it to turn on when you put it in reverse

reverse wire is for the backup camera polarity signal. The unit will still work if your VEHICLE SPEED SENSOR wire isnt hooked up. If you want a more accurate reading besides the GPS antenna. I suggest to hook up the wire.

mab6680, thanks for the info.  I don't plan to connect a backup camera to the NEX since my car already has one.

drenyce311, didn't know the unit still works without the VSS hooked up.  Luckily for me my car's factory harness has a pin for the VSS.

mines too. My harness had a VSS wire also