I think that they hit the nail on the head with everything that had actually 'happened'. The ending for that was great, with those still living able to leave, Hurley & Ben guarding the Island, and Jack sacrificing himself for the Island (and his eyes closing). However, the FS purgatory ruined the 'real' ending in my opinion, simply because it made everything else in the show FEEL unreal. Even though I knew everything that had happened, had indeed happened - the FS ending made it feel unreal and unimportant. It seems to me, that the writers were trying to satisfy both people of science, and people of faith - however ended up somewhat cheating the former, because it made what happened FEEL unreal and unimportant. Of course, for those of faith (or agnostic/sitting-on-the-fence...), it didn't matter what happened because everything was all fine and dandy in the FS. I think that they could have left the FS 'real' and still use it as a tool of consolation, without making it a sort of purgatory.
P.S. I'm not trying to unfairly stereotype the views of faith and science - I know people's opinions are effected by much more than that. Hope you all understand what I'm saying.
P.P.S. The Jack-John fight was awesome.