
Not only do the best cowboys have daddy issues, they worry incessantly about the kind of father they would be.
The flash-sideways (FS) of Lighthouse continues the pattern of taking us into the psyche of a beloved Lostie, in this case some thoughts and concerns Jack harbored throughout his life.
The introduction of David, Jack's son in the FS, was one of the most controversial aspects of Season 6. After the nature of the FS was revealed in the finale, some LOST fans went so far as to label the David storyline a long con, a waste of time.
My response: baloney.
Again I have to wonder how many people missed the point of the flash-sideways. Yes, it was a shared construct in a stage of the afterlife, but it was also an extension of the characters we knew and loved. Very few aspects of the FS exist without a basis in the lives which preceded it, and David is no exception. As of this review I can tell you that I'm a 35-year-old man who constantly wonders what kind of father I would be. Sometimes I love the images that come to mind, and sometimes the concept scares the living hell out of me — and I didn't even have the suffocating pressure that Jack endured from his father!
Lighthouse wasn't about David, it wasn't even about David's relationship with Jack. It was a deeper exploration of something that was close to Jack's heart when he was alive. That counts for something, and yes, that is legitimate character development.
On the island, Hurley leads Jack to a lighthouse along the coast at the behest of Jacob. It is there that Jack discovers Jacob's been watching the Candidates since their childhood, and he reacts by smashing the lighthouse mirrors. I'm not sure how plausible that reaction is; I'm pretty sure I would've been in awe and stayed in the lighthouse for hours snooping on people's childhoods.
Crazy Claire takes Jin and Justin to her makeshift hut, home of the famous Squirrel Baby. She patches up Jin's leg but has no such mercy on Justin. If you're keeping score, her on-screen body count is now up to 1.
Lighthouse is a rare case where I love the underlying concept and writing, but the visuals are so bland it nearly ruins the experience for me.

The first time around I thought it was simply a blast to see Jack in this father role, even if the FS were revealed to be nothing more than a what-if scenario. Matthew Fox had done just about everything else in the series except work opposite of children, so it was interesting to see him get humbled by his own son. Fox played it beautifully.
His two best scenes were arguably 1) his vow to David that he could never fail him, and 2) his enraged reaction to the lighthouse mirrors (even if it wasn't necessarily a realistic reaction).
I can't believe I'm saying this, but I think this was one of Jorge Garcia's best acting performances in the series, right behind The End and Everybody Loves Hugo. His scenes with Jacob, Dogen, and Jack are all pretty impressive, especially his tirade at Jacob near the end ("Mission unaccomplished!"). I think the difference is he wasn't reduced to well-timed "dude"s this time around, he actually had some meaningful dialogue to go along with his usual humor.
Dylan Minnette did a fine job as David, not giving in to the tendency to over-act like so many young actors do. There were a few brief occasions where he hammed up the facial expressions a tad, but overall he did well.
Deductions for Veronica Hamel (Margo Shephard), who needs to learn how to speak like a normal person and not enunciate every single syllable. Her robotic responses to Jack during a phone call were just plain awful.
Further deductions for Dayo Ade (Justin), who took an axe to the gut to spare us ALL the misery of having to listen to him.

Jack Bender's directing was great, as usual. The effects in the Lighthouse mirrors were very cool, almost chilling in some way. The CGI of the Lighthouse exterior — also very cool.
But here's the big problem with Lighthouse: it's way, way too bland and washed-out. The jungle is too bright, too bland, too pale, too dry. Some scenes, like the one where Jack encounters Kate by the river, actually washed out part of the screen with sunlight beaming off the water. There was absolutely no atmosphere in any of the outdoor scenes, which is completely the opposite of what I'd expect from LOST.
I'm not sure anyone's to blame here; it might've just been dry weather conditions or other factors beyond anyone's control. But several other episodes of S6 also have this problem, a lack of the deep shades of green and brown that once gave the jungle its lush, mysterious ambiance.
Deductions for the brief visit to the caves, which was a good idea on paper but poorly executed visually. The camera was in way too tight against Jack and Hurley as they revisited the coffin and Adam and Eve. There was no chance to be nostalgic because none of the shots captured any of the original atmosphere. If they didn't have the budget to re-create part of the caves they were better off avoiding it altogether.
Slight deductions for the actual Lighthouse set (with the mirrors). If they went through the trouble of creating an actual set for the bottom floor, they should've done something similar for the upper chamber. Anything to allow natural sunlight into the scene. You cannot replicate natural sunlight on a staged set and Lighthouse's finest moment suffers visually because of it.

I'm sad to say that despite my appreciation of the themes in Lighthouse I'm too often distracted by the poor visuals and pale scenery. The more I watch scenes in Claire's bone-dry hut, the more I watch Jack and Hurley go on their "old-school" trek through the crispy jungle, the more it makes me miss the atmosphere of earlier seasons.
The on-island storyline is significant in that it forces Jack to look inward after what he's witnessed at the lighthouse. Initially Jack was convinced his purpose in returning to the island was to carry out Faraday's plan. When that didn't work as he'd hoped he was essentially lost all over again. His experience at the lighthouse would help him regain that sense of purpose.

There were so many opportunities in Lighthouse for classic LOST atmosphere but they were all squandered. Heck, even throwing the sprinklers on for the Claire hut or the Lighthouse exterior would've added some depth. As it stands they all look like they're baking in the sun amongst patches of dying weeds.
The saving grace lies in the emotional impact of the flash-sideways. I'm not afraid to explore that dimension of the characters and I'm not opposed to being affected by what I see. It makes no difference to me whether David was real in retrospect, I was still moved by Jack's deep desire to connect with him.