This episode is not only full of resolution, but also marks the arrival of John Connor as a fully realized character. Previous to this point, it was easy to dismiss John Connor; he simply wasn't yet convincing as the leader of the future human crusade. Much of this episode could be seen as a retcon, but given how careful the writers have been since the pilot, it's entirely possible that this was the intention all along.
In fact, John's confrontation with Jesse nearly overshadowed every other aspect of the episode. I was so amazed by his demonstration of resolve, how well he had been keeping his cards so close to vest, that I was practically ready to download the entire second season and rewatch everything right then and there. John was so specific about his reasons for recognizing who Riley had to be that it should be easy enough to find those moments from those earlier episodes.
The writers have been taking their time with John, and while that has been frustrating at times, this is the right kind of payoff. It also serves to highlight the problem with all of this time travel and timeline manipulation. We simply don't know which "version" of the future everyone is from, and that means assumptions could be very, very wrong.
What we now know (after many hints) is that Jesse doesn't come from the same version of the future as John's father. John's father came from a future where John was winning the war. In Jesse's future, John is too close to the "metal", and this is leading to a slow but steady defeat. And to that the loss of an unborn child, and it's no surprise that Jesse would want to drive a wedge between John and Cameron.
It's not entirely clear which version of the future Derek comes from: a hopeful future in which John is winning, or a desperate future where John is out of his depth. And it's quite possible that there is a decision point that leads to one or the other, something that has yet to be revealed. All things being equal, one would expect that it has something to do with someone we already know: Sarah, Derek, or Cameron. It may be that this will come into play before the end of the season.
The titular last voyage of the Jimmy Carter does more than just provide a basis for Jesse's motivations. It might also prove out a theory that I've had since the beginning of the season. Could the T-1000 seen in the Jimmy Carter, the one that John was trying to forge an alliance with, the same one that has become Catherine Weaver? If so, then it lends much credence to the theory that Weaver represents a splinter group within SkyNet. It would explain why Weaver wants to incorporate human ethics into the aborning John Henry, despite her bloodthirsty ways.
Right down to John's final emotional outlet in his mother's lap at the end of the episode, this was easily one of the best of the season. It gives me great hope that the season will end on a high note. Even if the series comes to a premature end in a few short weeks, the writers have outdone themselves.t