The season premiere was mostly about the struggle to save Atlantis, and the long string of circumstances leading into the heist of a ZPM from the Asuran homeworld. This installment is far more focused on the heist itself and the inevitable consequence for Elizabeth Weir. The matter of her survival is left completely ambiguous, which should help to mitigate her departure somewhat, but the end result was never in doubt.
The plot can be summed up in a few short words: Team Atlantis tries to steal something from the Replicators, and things go wrong. Weir gets to demonstrate her core strength by fooling Oberoth (the Asuran leader) long enough for the team to accomplish their mission (and redirect the Asurans against the Wraith), but little else in the story could be termed a surprise.
That's not to say that the episode was the television equivalent of light beer. This is not a disposable chapter in the Atlantis saga. Weir's loss to the team is a major blow, especially considering some of the underlying character arcs connected to her presence. Sheppard is the most affected by her loss, and this is depicted well. At times, especially during the final landing sequence, Sheppard looks numb, as if unable to comprehend the enormity of what has happened. In hindsight, the entire ordeal beginning with "First Strike" and ending in this episode is one of the most grueling experiences for the characters yet.
This episode is also something of a prelude to the well-publicized shift in status quo. Colonel Carter will be assigned to lead Team Atlantis after Weir's departure, and the seeds are planted in this episode. Carter is less abrasive in this episode than the premiere (and more humble, for that matter), but the writers should be careful to avoid portraying her as some kind of miraculous savior for the team. Weir was hardly the best commander in the universe, but the team is fairly effective and Carter should learn to appreciate that competence to keep the balance intact.
In the end, this is an action-packed episode that feels light on plot twists but packs an emotional punch. Fans of Elizabeth Weir will be sad to see her go, but she gets some great material and a proper send-off. The change may have been unnecessary, but given the state of the Stargate franchise these days, it's hardly a shock. With the state set for the change in command, the writers should finally have the chance to initiate the character arcs promised for the fourth season.