I used one to move all of my stuff from one location to another when I was switching houses, I can't really find any other practical use for them other than travelling in style though. They can only take me to places I can just as easily Fast Travel to, and they fly too high and too fast for that minigun to be very effective. Is there some use for them that I'm not seeing?

They're potentially useful when approaching locations that have enemies around. I'm saying potentially because you will attract a lot of attention and if you end up with your gun pointing in the wrong direction you're a sitting duck. Outside of that and traveling in style, the only real practical use is getting Danse to like you more.

I use them as a moving company. And the gain favor with Dense.

Fast travel breaks immersion imo. I use the Vertibird to fast travel without killing my immersion into the game.

I find it primarily useful for mass looting transportation, for instance, I go to the fish packaging facility regularly to loot all the trays, [censored]loads of aluminum, but it's always infested with high level synths (im lv 62 now) so I always go in Power Armor to both give me a boost in carryweight and to survive the onslaught.

they're also good for combative insertions.