In many ways, I did prefer this episode to Lockdown. This will no doubt cause some consternation amongst other fans. I will honest that in terms of its scale, action, intensity, acting and attention to the mythology of the show, Lockdown wins hands down. But S.O.S is a very personal, emotional episode, and Lost knows how to produce these kinds of episodes too.
From the first time we caught sight of them I did like them alot but never thought much about them because they never got much screen time. Thus, it is surprising, firstly, that they should, out of nowhere, get a whole episode. Secondly, it is amazing that their backstory connects to the ongoing mythology. For those that still insist that nothing happened in this episode and that it was all filler, were you watching the same episode, I ask you? It is not a "Lockdown" episode, for sure, but it holds more mystery than any of Kate's episodes put together, for example.
The mythology referenced in this episode is more subtle than in other episodes. There is no DHARMA Initiative, orientation films, The Others [except a little of Henry Gale] or smoke monsters. It is similar to how the Season 1 episode, "Deus Ex Machina" approached the mystery of the island. It is the metaphysical and psychological approach which made the Season 1 episode and this one work so well.
It could have been so much less than what was shown. We could have been subjected to 42 minutes of Bernard trying to fish for Pearls and Rose doing a whole bulging basket of laundry, but it is smart that the writers decided to give these two seriously underused characters so many layers.
So we find out that Rose has an on-island connection to Locke. Now that is a first. Most of our character connections are off-island in some way. This plot thread harks back to Locke's first episode where we learn that his legs are healed by the island. Rose's cancer has also supposedly been cured by the island and explains her calm, fearless attitude towards her new surroundings.
Because of this connection S.O.S. is as much a Rose episode as it is a Bernard and Rose episode, but Bernard helps to carry it along and give it much emotional depth, as well as some wonderful comic relief. Perhaps the funniest moment was when we learn that he is a dentist, yet when we see his mouth he has worse teeth than probably most of his patients!!
The scenes between them when Rose confesses her secret to Bernard is heartwrenching and beautiful. But there is even more besides Bernard and Rose to engross in: Jack and Kate getting caught in a net, Jack shouting at The Line [wonderful camera work, by the way], Henry Gale being increasingly creepy, Locke's faith restored and the reappearance of Michael "Waaaaaalt!" Dawson. Because of everything that happens in this episode you get your money's worth and that is also why this episode is special!