I was really confused/disappointed with this episode. I expected to see what actually happened to the hatch and have some closure, the hatch was a massive part of season 2, and now they have just written it off with any real explanation.

I think that what we seen was all in Desmonds head, it did happen before he came to the island..but this was him dreaming it again with the knowledge that he was on the island and he did push the buttons etc...but that doesn't explain why he can now suddenly see into the future.

It's kind of like Charlies dream where people on the island and part of his life back home were part of the baby jesus' birth scene, and Lockes dream about having to find ecko.