I sat down to write this right after the finale, but I found that I couldn't. After a few days to process, I can definitely say that LOST had a very fitting and satisfying series finale. It was frustrating, interesting, provocative, infuriating, and touching, everything that LOST was.
For me, what I liked the most was the message in the finale: Just let it go. While it works as a message for the main characters (especially Jack), it's also a sly message to all the fans out there watching.
What was the Island? What was Dharma doing? Where did Jacob come from? Why was Walt special? Who were The Others? Every question you could have was answered with that simple message in the finale:
Let it go.
It's funny, coming from me, because I've been adamant that the only thing LOST had going for it was the plot. While some of the characters were interesting, they never really engaged me in a way to make me care (with the exception of Desmond). The problem was that everyone on that island was an asshole, and very few had redeeming features that made me want to root for them. But somehow during the finale that all changed.
As the finale progressed I cared less and less about the unanswered questions and more about these people finding their true happiness. It made me realize that in six seasons it was very rare to see the characters be happy and it was about time that there was a smile infection.
Story wise, I think everyone ended up where they should be. Katie finally looked beyond herself and reached out to save Claire. Claire will finally get to be the mother that she always wanted to be, but with a family that she sorely needed. Sawyer, well, Sawyer got out so he can star in a buddy cop show with Miles.
And In the end, Jack fulfilled his purpose, fixing the island by performing a hard reboot, and left Hurley and Ben in charge for years until they found a suitable replacement, like Jacob and his predecessors did. The island is still around being weird, but it's done with everyone we care about so it's time for us to leave too.
Like Christian Shepard said: It's time to let go.