It's just as heavy and fast as a minigun.
Its heaviness is just use to help balance it. I remember the Bozar from Fallout 2 and I know how overpowered it was, so I know why they made it that heavy. I'm not sure why it's so fast though but I didn't even need to read that article on the wiki at first to know that it's an automatic sniper rifle.
Messages to tell you to continue with the main plot, with a creepy/high quality picture of the guy who gives you the healing powders. If you wait long enough, it will go to 5 and the enclave quest line will begin.
Yeah they were really scary at my first playthrough, but creepiness decreased overtime.