There are at least two reports of this being used in Ukraine that I can recall, at Donetsk Airport and again at Debaltseve, with one destroyed near Donetsk AP.
Ukie propaganda called it a “thermobaric” weapon, which it isn’t.
It has a HUGE drawback, that being it has a VERY short range, 500-3000 meters, depending on the type of rocket, and has to get really close to the target to be effective.
But, when you can get close enough to shoot, it’s catastrophic. Some rsourcess credit this system with finally flushing the Right Sector out of the Donetsk Airport Terminal.
Vid of the TOS-1 in action:
https://www.youtube.com/watch?v=WfacUxfJbFI
The TOS-1A fields rockets of considerably greater range (about 6km).