A random observation: "deus ex machina" is, I suspect, very apt. It's not God -- "it" doesn't like being called that, we're told right at the end.

It makes me think of Asimov's "The Last Question", for some reason. So ... god out of the machine? God _is_ a machine (maybe).

On the whole, I thought the finale ended well. More importantly, it was told well, because it brought the focus onto the characters and their journey, temporal and spiritual. To me, this was always the central aspect of the show. The "mysteries" were something a lot of people were into, and to some degree the writers kind of fed that mentality, but it was really the story of the characters for me.

I know a lot of people wanted a lot more action, a lot more explicit closure, or what have you, but for me this felt like a fairly bold tack to take against prevailing opinion.

I'm told the LOST writers have said that it's not purgatory and they're not all dead and just don't know it.

As to LIFE ON MARS, as I recall, in the original British series, it was "all just a dream", but they were, I guess, "true" dreams. The character really did live back then, somehow, and then did wake up again in the present. IIRC, the follow-up British series references what happens to him after that point (in short: nothing good.)