This might also connect with the Egyptian myth of Ammit, a creature that devours those found unworthy. If one considers the possibility that Jacob is, or has become, something akin to Anubis, then perhaps that explains why Cerberus acts like Ammit. (Alternatively, Jacob may represent Osiris, and Richard may represent Anubis.) Why Cerberus would be called a "security system", or give off mechanical noises, is still not clear.
It's interesting to note that Alex was actually a part of the reason why Ben chose to oppose Charles Widmore and drive him off the island. At least, that is the implication. If Richard's careful inspection of the argument between Ben and Widmore over Alex is any indication, there was already tension between them. Widmore probably knew that Ben was a potential threat to take over as leader of the Others. Alex's right to live becomes the focal point in their contest to see who understands or receives the will of the island/Jacob more powerfully or sincerely.
The fact that Widmore is ultimately proven right is an interesting observation: Ben was forced to make a choice between the island and Alex. Does that mean that the island did not originally want Widmore ousted? Or was it that the island wanted Ben to take temporary control, but ensured that Ben's replacement by Locke was preordained by Ben's own decision to save Alex? It seems that everything was thrown off course by Locke's lack of self-confidence.
Considering all the hints to the contrary, it's surprising that Ben didn't kill Penny and/or Charlie. It seems he felt a connection between his decision not to kill Danielle and Alex and Penny and Charlie. The metaphor wasn't necessarily perfect, but it was enough to explain why Ben was musing over his past with Alex and his emotions over being responsible for her death. It provides emotional context to Ben's decision to return to the island without his vengeance. Because he realizes that he shares responsibility for Alex's death, he no longer deems it necessary to kill Penny. (That's unlikely to stop Desmond from coming after Ben, of course.)
As notable as this episode was for Ben, it was equally notable for John Locke. Ever since the beginning of the series, Locke has tried to convince himself and everyone else that he had a destiny, and that there was a reason he had come to the island. That turned out to be true, but he had to die and come back to life for his sense of destiny and purpose to be realized. Now he doesn't doubt himself at all, and it's both wonderful and terrifying. It should be very interesting if and when Jack and Locke are reunited.
Seemingly unrelated to the rest of the events, Ilana's apparent true purpose is taking shape. It has always felt like Ilana's presence was a sign of something more, and given Widmore's ongoing attempts to find the island, one would assume that is her employer. After all, it has already been hinted that Widmore was behind the crash of Oceanic 815 (at least, ensuring the plane was off-course in the anticipated vicinity of the island), so it's hardly a stretch to think that the Ajira 316 crash wasn't also his doing. (One might assume, from "Jughead", that the bomb is the object lying in the shadow of the statue.)
Overall, this was one of the best episodes of the season, focusing tightly on one of the key relationships in the series and shedding light on some of the key mysteries. The writers continue to peel back the layers of the story and inform much of what has come before, while perfectly setting the stage for the grand resolution still to come.