I actually used it a litte bit ago. I was watching some national news on PBS and the TV played an alert and I remembered you had posted that site. I was lookng at the NWS radar display and it hadn't updated yet with the warning but that site had. I wanted to see the polygon. It was north of me, just rain here. There was some lightning around, but the neighbor's kids were in the pool. Dumb.
Last night I was using the NWS display. My niece had some tornadoes around her, but they made out good. She asked me to keep an eye on things too, though they stayed up all night. I did call her when one got to be a few miles from her, though in the end there were just some trees down within a few miles I think from maybe just straight line winds.
In addition to the NWS display for tornado warnings. https://radar.weather.gov Though I guess sometimes it is just a little bit slow with those warnings.