The fact that MIB was pretending to be Christian to both Jack & Claire is interesting, especially because Claire was with Christian in Jacob's cabin.
Dez wasn't killed by Sayid but Dez did "wake him up".
Something explosive is going to happen in that hospital when they're all together. Sun "woke up" at the sight of John Locke (although she seemed terrified for some reason) and was suddenly able to speak English once again.
I thought it was a very good episode but it seems like some people are wanting answers more quickly than the producers are revealing them.
Keep in mind that May 4th's episode won't have anything to do with the Lostie's. It's supposed to be all about Jacob and the MIB. I imagine that May 18th's episode will set everything up for the finale.