I've used one (in training). Works great, nice clean cuts, but still a little slow. Quicker to just use an axe which, if you're a firefighter, you have handy. (Carefully chop around the perimeter of the windshield or side window. Use gentle blows to minimize dispersion of broken glass within the cabin.)
Okay now I'm imagining a classical ballet recreation of the "Heeere's Johnny" scene. With firemen.
Expensive, and pretty bulky to carry around along with an impact driver. There are less expensive, more compact hand-operated tools, e.g.: