I guess it shouldn't come as any surprise, but unless you were really really into Fallout 4 and just wanted even more content, don't buy this game. After 10+ hours it's very clear that this is basically an old-school expansion (you know, when they actually built on the mechanics of the game), but it's a half-baked one. I've had the game both freeze and crash, there's an early quest that's just broken, there's severe performance issues (seemingly network related) and there's multiple issues with the settings (lack of, and not properly saving).
Most damningly though, as far as I can tell the added multiplayer does nothing to add to the experience. Sure, you're playing the game with friends, which always makes things better, but the way it's implemented is about as generic as possible. There's nothing new or interesting going on here. It just comes off as if they made it multiplayer for the sake of being multiplayer, and just filled in the blanks for what being multiplayer means.
Having that said though, if you wanted more Fallout 4 it delivers, at least to an acceptable degree (even more so if you were into hardcore mode). And so far that's been enough for me. Already it's having the good old Bethesda feel of sucking to begin with and then getting more and more enjoyable as you go along. There's a ton of stuff people are gonna nit-pick to hell about this game, but it still delivers the same roam around in the wilderness experience their games tend to focus on.