Ok, I've had a few hours to think about it and I'm both pleased with the ending and also have my gripes. The ending only seemed to tie up seasons five and six, and plot elements that only appeared within seasons five and six. I mean, yes, there was a loop with Jack dying where he originally woke up etc. But I just feel that we've only had an ending for two seasons of a show, the other three/four seasons could have gone anywhere.
I really don't know right now, maybe it will take a bit of time to sink in but I enjoyed this finale for what it was but I just don't feel it 'fit' properly in some way.