The 2182 thread inspired this thought:
For as long as I have had a VHF DSC radio, and it has been since about since they got invented, it has gone off exactly ONE time with an ALL SHIPS that turned out to be someone screwing around and hitting the wrong menu choice.
I have heard a fair number of distress calls and NONE of them EVER were on DSC.
Also experimenting with calling between the boat and the tender and using it to track the position of the tender, the DSC functions always seem to die off while we still are in voice range. How useful has this actually been real world?
I can’t really speak to HF DSC that much except that on the low budget WAFI end of the system a surprising number of SSBs got installed without the second antenna 
Almost forgot - The local CG will NOT respond to the universal MMSI for the CG, you have to use their specific number. Drove me nuts doing DSC tests until I figured it out.
Fellow WAFI here - in our wanderings both West and East coast US, until this past fall we had received only one DSC distress call (accidental, off Oregon) - but last October we heard two different distress calls (one real and one might have been the CG Aux screwing around) in LI Sound - and this year we’ve heard three here in the Chesapeake (one accidental, two real but not really emergencies). We’ve also monitored several AIS MOB alarms (all accidental), which are supremely annoying with our MFD because getting it to shut up is a multi-step process - EVERY TIME the stupid beacon goes off!
It IS amusing to hear someone being run off of 16 decide to go to Channel 70 - which somehow doesn’t work 
We don’t have HF DSC, but I’ve never heard (first hand) of anyone actually receiving an HF DSC call.
if we ever get the other part of dsc and ais, like some port offices have, it will allow you to call a vessel from a click on the screen.
That will be useful
( South China sea it all goes off all the time)
I could do that with the right kind of display. Some chartplotters will interface with some VHFs to DSC call an AIS target by clicking on it. Mine is too old for that
I have had foreign survey vessels in the Gulf of Mexico hall me on VHF DSC to switch me to their working channel.
Before final retirement to SWFL in 2016, we recreationally boated and fished the Chesapeake Bay and offshore out to 75nm. With 28 years in the USN, most of my 21 commissioned years in Norfolk, and over 13 years at sea, I was very familiar with the offshore area, the approach routes, and the shipping channels.
Being an attentive mariner, it was always a challenge to hail on VHF 13/16 with “…merchant ship inbound Thimble Shoal Channel vicinity buoy xx I’m the xxxx at 2nm off your stbd bow…”. Usually no response at all. But once I updated one of my VHF radios to include AIS receive, all I had to do was touch the symbol on my MFD and the call was placed to that specific vessel, and I knew the name of the vessel I was calling. Made it so much easier for me to make it clear to them that I was NOT some WAFI who was going to disappear under their bow.
As a fisherman, we used DSC position requests and reports to selected friends when fishing in the Bay or offshore to call them in on the bite. As simple as placing a call to a vessel in your “phone book” by MMSI number.
While offshore VaBch and then in the GOM, I have received at least two dozen DSC distress alerts on the VHF. With the NMEA 2000 connection to the MFD it would be immediately plotted so I could see the position of the distressed vessel - IF they had positional info provided to their VHF (too many don’t).
Sorry if I took this off topic a bit.