Most other series that have played with alternate timelines and changing history and transplanting memory and so forth has ultimately returned each character to the "real" or original version of themselves. The implication is always: people must be themselves, and all meaningful actions and choices proceed from that insistence on unique self-identity.
Fringe as a series rejects that. Character identity is mixed-up, messy, often to the point of being non-sensical. What is primary is relationships, the choices we make about the people we care for, and the new choices that become possible because those people are present in our lives. Everything else proceeds from that. And solving the problem of the Observers -- who are defined by having lost the ability to form these connections -- was really a perfect way for Fringe to conclude.
Reblogging myself by way of the last TV Fanatic Fringe roundtable.