We have so far found no need or value in adding AIS. Not that we don't feel the technology is great and can be extremely useful in some areas and situations. But so far we have not seen any need for it in the boating we do and the areas we do it in.
We don't run at night because of all the crap in the water in the San Juan's north into BC (don't know about the south Sound- our boat refuses to go there
).
If the visibility is poor and we are in a commercial shipping area we use Seattle, Victoria, or Vancouver VTS to be informed of potential traffic conflicts and to have the commercial vessels informed of our whereabouts and intentions. We are told that this makes the commercial folks a lot more aware of us and our whereabouts as opposed to hoping they'll notice us on their AIS displays unless we get real close and they're running a proximity alarm.
We do have an AIS receiver application in our iPad but so far its only value has been to tell us the "name of that ship over there."
We have a very good radar and monitor it all the time even in good visibility. So when the visibility drops we have no problem transitioning " to instruments" since we're running the boat that way anyway. So between the radar and VTS we have yet to be "surprised" by other traffic.
We do have a hole in our panel to fill. Right now it's occupied by a very good Furuno Loran-C unit that came with the boat. The three candidates for this spot are a second VHF, a weather (wind speed/direction) display, or an AIS.
The AIS is a very distant third. We just don't see it is contributing any information that we really need to know right now and we cannot conceive of any situation in our future boating here or on up into SE Alaska in which AIS would be important to have.
So, cool toy, valuable to have in confined waters like the ICW perhaps where there is lots of traffic, but it's nothing we view (so far) as being essential to recreational boating in this area. The prices have come down a lot but we'd rather put the money in the fuel tank.