I put a "B" transponder on my Tartan as a black box from Simrad. I have been hailed by name on the Sabine and Mississippi Rivers by guys who not only outweigh me but are steelclad also. But that's not the reason we bought it. I attached it to my Standard Horizon VHF and it displays who's around me on the RAM microphone. So I can get on the radio and say "Tug Brown Water 4, this is Impetuous on your starboard bow. We are slowing down to allow you to cross ahead of our vessel."
We have used the AIS to know what is coming around the blind curve in the GICW, to let the tugs know our intentions and I check it occasionally on Marinetraffic.com to see if she is still in her slip at home.
Down on the Gulf Coast, the shrimp boats not only don't have AIS but they also don't maintain a radio watch on the VHF. So you just have to dodge them.