I wouldn't say it's completely useless, there's just only a handful of situations it can safely be used in. I remember, the first time I ever used it, I was somewhere out in the wasteland near a big crevice with a bunch of super mutants all over the cliffs. Whipped that thing out, aimed high, and let it go. I've never seen so many super mutants get obliterated so fast before.
I used it once to wipe out that respawning Enclave camp that appears on the road between Megaton and the Super Duper Mart after you complete Waters of Life. I just wanted to see the earth-shattering Ka-BOOM! I reloaded a previous save after using it.
i carpet bombed evergreen mills with it, then shot it down at my feet to see how high i could go.
I like to use it at the Drive-Ins, and other places with abandoned vehicles and Raiders. I need to use it in front of GNR