I have to agree on this one. While I understand that there are no light sources anymore in the 'visited/seen' places on the map, it's really BAD from a usability/players perspective to hide it in plain black. It is realistic to the extreme and doesn't (in my humble opinion) reflect what players would expect (but I might be wrong, this is my player's view on it).
Ultimately it's going to be very frustrating to players to have Lighting on and us GMs are likely to turn it off (since it's unusable) UNLESS there is ambient light on the whole map (which might not be possible in many circumstances like caves for instance).