If anyone had problems with "The Last Sam Weiss" before the last minute or so, they probably changed their mind. The episode doesn't move very fast and a lot of the dialogue is mired in "mysteriousness," with Sam Weiss talking about the previous Sams and Peter looking for his father, the Secretary of Defense. Because the characters themselves are wading into unknown territory, the writers have significant leeway over how things play out and not everything has to make sense at first, though we may never get some of the answers we're looking for.
Then the ending hits--Peter entering the machine after Olivia turns the other one off. We see a montage of Peter's life and he steps into the machine--and an apocalyptic future where everything has gone amok and Fringe division is trying to keep things under control.
Score: 9.0/10