So I beat it for the first time a little bit ago. The ending quest is epic as fuck, kind of like the Liberty Prime sequence from Fallout 3, but actually good, because you get to do something, and the last boss isn't some pushover in a lab coat, this guy fucks you the hell up, at least the guy I fought did. I have no idea how many ways this ending sequence can play out, honestly. Just from the series of choices I was presented leading up to the point of no return quest, I could see a number of ways it could have played out, let alone if I had, for instance, been a full on Legion supporter, or something like that. The number of ending cards is nuts. Pretty much every notable quest chain is touched upon, and I don't mean notable like mandatory for a particular path, I mean notable for having more than three or so parts to it.
I'm definitely going to revert to an earlier save and explore more of the options available just in my end game, but I can already see a bunch of different ways I could have gotten here. The quest content in this thing is fucking bananas.