The vagina monster is a bit before the ending. I did find it interesting that the Vault was a lie, but hey, you saved the world sorta! Check out Playthrough 2, you'll fight tougher enemies and get better loot. Its still lots of fun!
But Honestly,
Spoiler
The ending was weak. They never touch on the players background and nothing is explained. i had fun but I think the game just fell flat at the end. Everything got insanely rushed. Maybe DLC will fix that, but it shouldn't have to.
If we hit that bull's eye, the rest of the dominoes will fall like a house of cards. Checkmate.