and I have confirmed 13nm by hailing another AIS vessel using VHF. I estimate our Class B range is 10-15, maybe as far as 20 if it's a larger ship and their antenna is high. I'll pick up large ships with Class A AIS transponders before they notice me.

For coastal situations that's fine with me, as we're generally keeping more or less constant watch and don't worry until we're on a closing course with close-in vessels. If I was worried about a ship I'd hail them on VHF to make sure they see us. That's the biggest benefit about AIS -- the ability to hail by name (and see their COG and speed) when you can't visually read the ship name.

I also like that is displays Closest Point of Approach (CPA) and highlights vessels in red that will come within my selectable guard zone (I use 1/4 mile).