Just finished it. Sobbed uncontrollably starting at Christian appearing for Jack through the end. That ending was a fucking gift, a beautiful present neatly wrapped and ribbonned for this fan here. I don't feel like I was smacked in the face with answers, but at the same time I feel that they inadvertently cleared up most of the bigger questions I had going into the show to begin with. Everything else is a great detail in comparison and I'm glad that they didn't waste their 2.5 hours going "okay, this is what that was" and so on.
The battle sequence between Jack and the Man in Black was absolutely fucking incredible. The scenery, Giacchino, Bender's direction-- it felt like a great, epic battle scene from any great film. Extra kudos to them for actually having Jack getting stabbed, and showing the knife trying to slowly cut his throat open. That shit was fucking raw and unexpected. Jack and Kate's kiss and farewell was pitch-perfect and satisfying. Every "awakening" sequence was phenomenal, particularly Charlie and Claire. Wow. I kind of wish that Hurley and Charlie had a better scene of them remembering one another, but Garcia's shit eating grin was fine I suppose.
I have several solid ideas about what I think the island ultimately was, and before the finale I couldn't have formed those ideas at all. When I first started watching the show, the biggest mystery for me was simply what the island was. Learning about its past and seeing what the characters who stumble upon the island was all fine and dandy and not every bit of it needed to be cleared up, but the finale gave me just enough to say, okay, I'm pretty sure I understand what the island is. What I haven't quite figured out exactly is what happened at the end but I'm okay with that as I fully plan on watching the entire series again when its released together on Blu-ray.
I'll have more later, but that was absolutely god damned amazing.