I only use it to see what's going on at farther than normal vis range. I never use it for firing as imo if you're zooming in to get hits you're probably too far away to be firing at all (other than a long 6 plink). And as others have said--it ruins your SA as your field of view is now tiny in comparison to normal view.
I just wish there was a way to configure a zoom setting other than the default one, which for me, for most purposes, is too much. I'll hit zoom and then zoom it out to my liking. Something like half the default zoom. After that it'll stay at that range the rest of the that session of the game. It's not like a head position that can be saved with F10.