From the very beginning with Lost, you hang onto the characters and Oscar-winner Michael Giacchino's score for dear life and suspend disbelief. It never did make any sense! (The NYorker profiles Oscar-winner Giacchino; see clip below.)
Even so, while the finale worked for me to a degree (there was one soppy moment with Benjamin Linus that went too far), I was confused. When Jack closes his eye at the end, is his life flashing before his eyes? (Obviously, much of the show was shown from many other points-of-view.) According to ABC, when Jack died, he joined a group of already-dead people in this transitional space, and was joined by others as they also died, before they could all move on. It turns out that they weren't all dead from the time of the first airline crash.
That misapprehension came about because ABC misled a lot of folks by hamfistedly sticking in one last shot of the Oceanic 815 plane wreckage as transitional filler. This caused LAT writer Mary McNamara to get the whole thing wrong; the LAT followed up with another story reflecting ABC's clarifying email. Someone at ABC is in trouble with exec producers Damon Lindelof and Carlton Cuse, who have enough 'splaining to do without somebody else making it worse! (Television without Pity has a recap.)
Here's a selection of folks on the finale: David Chute; EW's Ken Tucker and Lost expert Jeff Jensen, Movieline's attempt to tie up the loose ends opened up by the video below; and a more serious approach byErin Andrew and MTV. (I still want to know: why did Jack, who was supposed to protect the island's power-light, want Desmond to mess with it--in order to render the smoke monster mortal? Is the baby Claire gave birth to twice also dead? And why does Jack have a son in the transitional space?)