A highly critical blog from Slate on the ending.... shares the same interpretation of sideways world, but quite bitter about it, and I see their point, even though I am still happy with the ending.
Lost: The bomb did not work. (53) - By Chadwick Matlin, Jack Shafer, and Seth Stevenson - Slate Magazine
I dont' share his opinion at all. I have thought about the Ep even more than I did from my first post. IMO...a HAPPY ENDING. Isn't that the way good stories should have????