i liked the ending. personally maybe i'd have liked it more if there was more o'quinn/emerson/cusick going on and less slow-music couples action...
but i did write up these thoughts and thought that maybe people would be interested in reading them:
The producers have Lost have stated on many occasions that the show was really about the characters.
Samuel R Delany's book, Trouble On Triton: An Ambiguous Heterotopia, centers on the story of a character named Bron, in the far future. In this story, there is an interplanetary war that is going on, but Bron is not affected in any direct way by the war - in happens in the background. The reader is never told any great details about this war - only those aspects of it which affect Bron.
Likewise, in Lost, there are many mysteries. Who caused some of them to time travel? What effect did Jacob really have on their lives? What was the island? How was Walt special?
In the form of narrative that Lost has decided to use, these questions are not relevant, however interesting they might be. The answers to these questions are never learned by the characters, and are only as relevant to telling the story that the producers want to tell as explaining the inner workings of an automobile engine would be relevant to telling the story in any movie involving cars. The answers may be interesting, but are not strictly necessary.
One of Lost's narrative devices is to have every piece of information imparted to the viewer through the voice of characters. Nothing is stated objectively, and the viewer must decide for themselves how much of what the characters have said they wish to believe. The character of Jacob claims that the island is necessary for the world to exist, but we have only his word to take for it - the story would play out exactly the same whether this were true or not. Again, this story is not about the island, it is about the characters. Specifically, given the opening and closing scenes, it is about Jack Shephard's journey.