That was my understanding as well, that at the end of the finale, everyone was "dead"...but that they passed on at different times in their lives. I think Christian says something to the extent of "some before you, some well after you" to Jack, and saying that there is no "now" where they are now. Overall, I was pretty happy with the finale. I have seen and heard a lot of people strongly disliking it, but that is to be expected. Rarely do you see a television show or movie that isn't complained about in one way or another these days (especially with the internet), and it is nearly impossible to please everyone. I can understand why some might be disappointed in the lack of explanations relating to the island itself, as well as a few other things (Walt's "powers", what happened to each individually after they left the island, etc.)...but to me, the episode itself was pretty good I thought.
There's a pretty good recap (and thoughts) from "Doc Jensen", a somewhat well-known LOST fan/blogger over at EW.com that I think is pretty good. I've still got the finale on the DVR, and hope to watch it again or a couple more times just to get it all to sink in. I've thought about going through the whole series on DVD again too, but we'll see if we can get to that over the summer or not. My wife and I were just talking about those who may catch up on the series on DVD now, and that would be cool...but I do think you maybe lose part of the experience (particularly in the early season) without having that week of anticipation between each episode. I remember us talking about it all week and waiting for what came next. Anyways, I thought it was a pretty good finale to a great series. I know that I'll really miss it, and although I'm glad they set an end point for the show, I'm sort of sad that it is all done. Sort of like when ROTS hit theaters....a lot of excitement to see the "last Star Wars movie", but sort of bittersweet since its life on the big screen (aside from animated CW) was over.