Let's dive straight into the main event in this episode: the death of four main characters (although there is a slight question mark over Frank). I'm all for killing off main characters as, when handled right, it adds to the drama, can be very emotional and is a great way of provoking an emotional response from your audience. That is of course when it's handled right; here however it wasn't.
I can't help feeling that the main reason for killing off these characters was simply to thin out the numbers so the other characters can be focused on in the last few episodes. This for me completely undermines the deaths. Sun and Jin had been mainly just sitting around this season with their main purpose being to find each other. So now that they have it seems the writing staff have no other ideas for them and so kill them off. They don't even get one full episode together before they're unceremoniously drowned. Of all the characters on Lost you really wanted these two to have a happy ending, especially after fake killing Jin about three times, to finally do it seems bad form. Of course you could argue that as I'm clearly so annoyed by this decision then it did its job in creating an emotional response. However after rewatching the episode and giving it a few days it still didn't work for me. Jin's decision to stay felt more than a structural thing than a character thing. By which I mean the logical thing would've been to leave her to survive for their child; but the two have been apart from each other and come back again so many times that doing it again would've been retreading old ground.
Then there's Frank who (assuming he is dead) seems to have gone out the same way as Illana. He had no real contribution to the season and so it only seems like he was a main character because he would've been sitting around anyway. As a nice guy dragged into the plot killing him off in this manner was very poorly done as well as a waste of a good character. That said I will concede that Sayid's death was cool. After acting funny for most of the season to have him go out in a fireball of redemption was a good way to end his story.
Of course there was 40 minutes of this episode before the killing spree, most of which was good. This week's flash-sideways was another Jack story. The twist being that it was really Locke's story just seen through Jack's eyes. The reveal of how Locke ended up in a wheelchair in this reality was nicely done. While it was a shame we didn't get to see the actual plane crash, seeing his catatonic father was a great and very sad visual. It gave enough without needing exposition that Locke could fill in the rest later and the fantastic performance from Terry O'Quinn was just the icing on the cake. Also it's interesting to note that Lost is such an impressive show that they can get a fairly big TV actor like Kevin Tighe to come to Hawaii just sit in a chair for a single scene. This is one of those times where being a big budget show really helps as using a body double for that scene really wouldn't have worked.
On the island there was a lot to like too. Sun and Jin did get a couple of nice scenes together, even if they are undermined by their poorly executed deaths. Also we got a bit more black smoke action which, while not as impressive as some earlier actions scenes this season, was cool to see. And we now know Locke's end game is to find a way to kill all of the candidates. And then there was the shootout on the pier which had Kate get shot. It was probably meant to work as a way of showing that at this stage in the show no character is safe, although funnily enough I think actually showed that she'll survive. It'd be a bit daft to have her take a bullet that'll probably put her out of action for a while only to kill her shortly afterwards.
And despite my extreme dislike of how the scene ended, the stuff on the sub was very tense and very well done. I knew Jack was right about the bomb, but you couldn't blame Sawyer for not trusting him. We have the benefit of having seen the dynamite scene with Richard from earlier this season, Sawyer's seen nothing like that to make him believe in the island. And just to bring the review full circle I'll finish with one last word on the deaths. I can see the argument that having Locke kill off three of the candidates shows how dangerous he is and ups the stakes for the final few episodes, but I don't buy that myself. He's the bloody smoke monster! We already knew how bad-ass he was without needing to get rid of Sun and Jin without any decent emotional pay off.