
I remember the passionate debates in the LOST community months before LA X even aired. Some were ready for a "reset", i.e. the island stuff never happened. Some were convinced that we'd see split realities. Some were convinced Jughead didn't explode at all, that the island protected itself with another time-flash.
Only one thing was certain: lots of people were going to bitch no matter what path Damon and Carlton decided to take. I'm fortunate to be in the group that loves the decision they ultimately made. Season 6 is quite brilliant in that half of its content takes on a whole different meaning once you get to the end of your first watch; you almost have to watch it twice to fully appreciate the storytelling that's going on here.
But I'm getting ahead of myself.
LA X gives us our first glimpse of the flash-sideways (FS). Just as a heads-up: my S6 reviews will treat the FS as what it was revealed to be — a shared reality forged by the Losties between the stages of death and "moving on". I had absolutely no idea what it actually was until the very end of the finale. I was both shocked and overjoyed by it. So, just a fair warning... I think the concept is an elegant and beautiful one, thus many of my S6 reviews will be positive.
The first FS scene is one of my favorites, not just because it so closely mirrors a scene from Pilot but because it gives us a few gentle hints:
* During some rough turbulence on the flight, Jack clings to his armrest with a white-knuckle grip. Rose turns to him and says, "You can let go now." Beautiful. Some people have theorized that the turbulence was the actual moment Jack had died on the island, which isn't impossible since Juliet seemed to briefly slip in and out of the FS.
* When the turbulence finally subsides, Jack turns to Rose and says, "Looks like we made it." Rose gives him a smile that's not your ordinary kind gesture. It's a knowing smile. She finally replies, "It looks like we did."
* After Bernard returns from the bathroom and takes his seat next to Rose, she lovingly says, "I missed you." The first time around I thought that exchange was a little odd, borderline corny. Now that I know what the FS is it chokes me up just thinking about it.
The other FS scenes are head-scratchers the first time around, raising questions on what the heck's going on. There are plenty of similarities, yet just enough differences, compared to the "original" reality. Charlie nearly "dies" suffocating on a bag of heroin but Jack saves him. Kate's still beating the tar out of Marshal Mars and running away, except this time she inadvertently pulls Claire into her escape attempt.
On the island, Ben puts the pieces together to figure out what Locke really is. I guess it was obvious after Smokey destroyed Bram's team right in front of him.
Elsewhere, Jack's group find themselves at the imploded Swan in 2007. Juliet's somehow buried in the wreckage but calling for help, triggering a mad scramble to save her. Sayid's also hanging onto life by a thread, and thanks to a conversation with post-death Jacob, Hurley knows what must be done. Sayid is transported to the Temple and indeed saved, but not before he's apparently drowned and left for dead.
Quite the ambitious and chaotic start to Season 6.

Josh Holloway and Elizabeth Mitchell stole the early scenes on the island, with yet another heartbreaking farewell to Juliet and agonizing moment for Sawyer.
Michael Emerson and Terry O'Quinn did just as well at the other side of the island, especially TOQ in his transition to the new Man in Black. His expressions and mannerisms are now anything but ambiguous, mostly because he no longer needs the facade with Jacob dead.
On that subject, I've seen some LOST fans suggest Titus Welliver should've been cast as MiB throughout Season 6. I respectfully disagree. The fact that Locke, a beloved character for five seasons, is playing MiB creates a sense of cognitive dissonance you just wouldn't have with anyone else, especially a new face like Welliver's. I'm sure many Locke fans were just like me, holding out hope that "real" Locke would somehow overcome the evil occupant of his body. You don't get that added dimension with anyone else.
The main cast were very solid but I'm deducting points for Ken Leung. His first few lines in LA X were just terribly delivered ("Wha.. what? I can't hear you, are your ears ringing?"). Other minor guest roles were also unimpressive; deductions for stiff performances by airline security and especially the woman who discovers Kate in the bathroom ("Come quick! Come quick!").

The CGI sequence in the first flashback gets all kinds of grief from certain LOST fans but I didn't think it was all that bad. I think my only complaints involved the inclusion of the DHARMA shark (too on-the-nose) and the fact that everything seemed crystal clear under water. Just a bit of warping and attenuation would've gone a long way in that sequence.
The destruction of Bram's team in the statue was satisfying chaotic, particularly the first-person shot of Smokey stopping just short of Bram's circle of ash. Smokey might be evil but Bram was too smug for my tastes; I was glad to see him go.
I actually liked the set design of the Temple, claustrophobic as it was. Sure, certain parts might've looked TOO much like a constructed set, but the atmosphere and layout were effective despite the flaws of the storyline arc itself.

As is the case with most Season 6 episodes, LA X is actually growing on me as time passes. Now that I realize the FS scenes were far more carefully constructed than I gave credit for, it's a pleasure to go back and watch them under a different context.
The revival of Sayid in the Temple is significant in that it establishes a pervasive theme for S6, the idea that light and dark forces are continuously engaged in a battle within us. Just as MiB manipulated so many others when they were vulnerable (Locke, Ben, Claire, etc.), Sayid was now claimed and manipulated by "sickness", the ultimate state of hopelessness and despair.

The scenes in the statue were downright bone-chilling, thanks in part to the set design but also the expressions on TOQ's face. The moment he said "I want to go home" and his eyes turned cold I nearly soiled myself.
There was certainly an atmosphere to the flash-sideways, both before and after its nature was revealed in the finale. The first time around it just felt like one big, bizarre landscape, some kind of tenuous reality that was subject to decay. Since the finale, the atmosphere is quite different and very emotional. Just about every moment of LA X's flash-sideways are bittersweet, even something as mundane as a conversation between Boone and Locke on the plane.
The Exodus-like montage at the end of Part 1 is tremendously moving, even as we don't understand what world we're looking at just yet. There'd be plenty more moments like that in episodes to come.