SPOILERS!
It focused too much on the events of season 6, which itself was rather isolated from the first 5 seasons.
Agree that it didn't answer some of the major questions, and I grew really annoyed with that. The egyptian stuff for example. I very much doubt that Jacob built the Taweret statue, the temple and draw or carve the hieroglyphs all by himself, despite being on the Island for more than 200 years, lol.

I didn't like the Purgatory ending, but mostly because a whole bunch of characters weren't there (Michael, Mr Eko, Jacob to name a few), and mostly because Ashes To Ashes had a better Purgatory ending last Friday, lol.
Jack was too obvious to be replacing Jacob. I could see his death coming from a mile away, especially in the foreshadowing by Hurley in "What They Died For".
I wish the episode hadn't been spoiled for me now. :/