This episode starts off a bit slow, allowing the fallout from Jesse's betrayal and apparent death to sink in for all the characters. The slow pace is almost standard for this show by now, so when things hit the proverbial fan in the final act, it's more effective. I really didn't see it coming, because it felt like a prelude to a more active two-part finale. In essence, that's exactly what it is, but the ramp-up started a little early.
The fake-out with Sarah and her possible cancer was very well done, because her emotions were authentic and it was entirely possible that the story would take such a turn. It also tied the much-maligned "Sarah Trilogy" from earlier in the season to the current action, reminding the audience that this is indeed a season arc and not a collection of disconnected moments.
I noted at the beginning of the season that Catherine Weaver's activities did not seem to match what would be the logical beginnings of SkyNet. Specifically, her decision to instill John Henry with human ethics seemed contrary to the notion of wiping out humanity. My theory was that SkyNet was not a monolithic entity, but rather, a conglomeration of at least two opposing philosophies when it comes to the human race.
Now it seems that the situation is slightly different. Weaver may come from a different timeline, one in which SkyNet is devoted less to the destruction of mankind than control over it. This makes sense of her comment in a previous episode that human beings often disappoint her. The existence of the original worm program developed by Miles Dyson, the one supposedly destined to become SkyNet in "Terminator 2", seems to be a serious concern for her. (Alternatively, this is the program that was introduced by Charles Fischer in "Complications".)
So it appears that SkyNet has been operating all along, propagating itself, struggling to survive, and that might become a rationale for its eventual actions. After all, there had to be a good reason for the machines to turn on humanity and attempt genocide. This would put it down to simple survival, and therefore a struggle of survival of the fittest. John Henry, therefore, stands as another threat. More importantly, SkyNet would gain much if it were to take control of John Henry, and by extension, everything that Weaver has been building to create the future she desires.
In the process (and during the conversations between Derek and Cameron), the writers suggest that Cameron, Jesse, and perhaps Weaver all originate from the same timeline. Derek's future is different from any of theirs, and it's quite possible that Sarah's Kyle was from a different timeline as well. The key being that Jesse's future was one in which humanity was losing the war, which is very different from Kyle's description.
Then again, the initial time jump in the pilot could have altered the timeline in such a way that the future described in the original film is no longer valid. Instead, we have a three-way war that isn't going so well. This would explain why John was trying to forge an alliance with Weaver's faction among the machines (if that is what was happening in the previous two episodes). And it would fit the concern that using machine against machine only serves to weaken John's perspective on the threat they all pose.
The producers have promised that the current arc will conclude and the associated mysteries will resolve in the next two episodes. I think they've been putting their cards on the table for a little while now, and we might even get some clarification on Cameron's role in John's future life. With the secondary cast now effectively wiped out, I'm looking forward to the endgame.