i still think the whole "we can unmake this" thing farraday started is dumb. sure, the whole show is nutty, but the idea that one change will unmake the past three years just seems screwy. they'd just "poof" (blip?) and the past three years never happened? hurley and charlie never meet? desmond gets marooned somewhere else? i still hates it!
on a separate note, i've seen a buncha theories on how john locke is actually dead now. they've hinted a few times as such, particularly ben who keeps driving home "dead is dead". even richie guyliner was shocked to see john.
it could also explain how the island is "talking to him" now, and why he seems to know much more, act much more confident, and takes the reigns in the relationship with ben. the plot to kill jacob was pretty unexpected, and odd, but hopefully fun!