fuzzy inside - it think that's what they were going for
but once that fuzzy feeling wears off, and you start thinking about all the unanswered questions, won't you feel like they pulled a fast one on you?
i sure do.
in truth, the ending had nothing to do with the island, or even with the main story. and the flash-sidways had nothing to do with the bomb going off, like we wre lead to believe. really, we could ignore the whole flash-sideways timeline, it's not at all essential to the plot. all that comes of it is 'oh yay, they all get to see each other again and they all forgive one another for being murderous wretches'. great.
but what about the island? the light? the temple? the tunnels? jacob and mib's mother? walt's powers? (where is he by the way?) the electromagnetism? it all just floats out there, completely unexplained. ugh.