I believe AIS is on par with GPS as a useful technology. With RADAR and a chart, you could find your way in a nighttime fog, but with RADAR, GPS and AIS, you can find others, and naturally, you still have the paper chart for when the GPS goes wonky.*
Of course, AIS and GPS are frequently interlinked, so AIS data does not, in fact, replace deck watches, and if the AIS shows the only ship in 10 miles bearing away and the RADAR calls for a collision, believe the RADAR.
I personally think that the greatest value of AIS is to identify local traffic and to tell big ships where you are relative to their track. I have had conversations with lake freighters even in little Lake Ontario where they have not seen me on RADAR even when provided with a reciprocal bearing, although a good pair of binoculars usually reveals me or my lights.
To be fair, my steel boat apparently is visible to RADAR on either shore .
Anyway, my schoolmarmish tone is just to reinforce that AIS is cool, but not, as I have read in certain spots, a "replacement" for anything. It gives supplemental information to the usual careful watch that should be kept in any case.
*Anyone who thinks "it won't" or "it can't" hasn't watched the GPS co-ordinates wildly correct without warning, hasn't seen "tests" by the military alter the accuracy, again without warning, hasn't found their plot mysteriously cutting through a peninsula, or is someone who thinks the current solar surface "quiet period" will last, like the bull market, forever.