Used to teach sailing on SF Bay (Cass Sailing Marina, Sausalito). I remember all those times sailing in thick fog and nasty rainy conditions. Radar would be a very valuable addition.
For coastal cruising as well, radar is a wonderful tool. In fact, experienced navigators would likely rate it as the 3rd or 4th most important navigational tool aboard, after the compass and fathometer!
You can't really compare AIS to radar. AIS is a passive device which displays information about boats which transmit an AIS signal. Not all boats. In fact, only some large commercial vessels. Not fishing boats. Not yachts. Not runabouts. Not sailboats. Not buoys. Not islands or coasts or rocks. Not storm systems.
Guess as an older navigator I'm not much enchanted with AIS. For many, I think it could be a distraction, luring them into a sense of comfort by displaying information on a screen about SOME large vessels, while distracting them from using the most important navigational tool of all: the Mark I eyeball :-)