So... that was unexpectedly exactly how they thought the plan would work out.
That bothers me a bit. They didn't even address the possibility of it resetting all time because of how the Observers had interfered before the Invasion. As smart as Walter and Peter (not to mention Olivia, Astrid, and September) are, you'd think that would have occurred to one of them and they may have been hesitant/asked questions about it! Last night I thought that maybe it only reset to 2015 because that's when Walter was inoculated, but September inoculated himself in 2036 and Walter seemed to have no misgivings about that screwing up the plan. Granted, September couldn't go through with the plan because he was shot (sad face), but still.
So this is a crappy, underdeveloped theory, but I was thinking that maybe the reason why it didn't reset everything is because the interference of the Observers (or, more specifically, the interference of September) was emotionally-driven, even if he didn't recognize it at the time. He distracted Walternate for a reason I can't recall (maybe it wasn't explained), but he felt the need to save Peter and Walter from drowning to right the wrong he had done. To a degree, that's guilt, right? So maybe these better human beings that replaced the emotionally-devoid Observers interfered in emotional ways, allowing for the timeline to move in a very similar way, only this time not as a mistake, but on purpose. Maybe Walter helped insure that the timeline would move correctly, since he told Peter he was going to give him his life back. He could've puppet-mastered that to a degree, I suppose. Though when Peter was deleted from the timeline, I think it was explained by Walter that Peter was never saved from drowning, so that may just blow this theory into little pieces.
The finale was definitely emotional, especially the second part. About every Walter-Peter moment was tear-inducing. The tape part was very poignant, and Walter's "You are my favorite thing, Peter. My very favorite thing" really got me. So did the Walter and Astrid scene with Gene. So did Peter mouthing, "I love you, Dad" to Walter before he entered the wormhole (which I only just realized is in response to Walter's tape saying, "I don't want to say goodbye... but I will say, 'I love you, Son.'"). So did Peter swinging Etta around (though that didn't make me teary the first time I saw that scene). My father made a comment how sad it was that no one will know the sacrifice that Walter made. He would just be gone for no real reason.
Question: why doesn't Lincoln Lee have his adorable glasses anymore? He looks like Alternate Universe Lee instead of our Lee (maybe they have crazy eye-corrective surgery over there that he couldn't pass up). I wish we would have gotten to see Fauxlivia and him fall in love, though I am glad that we know they are married and have a son. I always liked Alt. Lincoln and how he acted towards Fauxlivia. He was a little more outgoing than our Lincoln, so I'm sure the story of our Lincoln and Fauxlivia falling in love would have been very sweet. Guess they're leaving that to fan fictions.
One last thing: Cortexiphan Olivia is hardcore.