It's gonna take a rewatch before I totally digest it, but for the most part I was not disappointed. I may have overanalyzed some parts (which for Lost is pretty hard to do) but I'll give them a few episodes to explain stuff before I start nitpicking.
One thing I did like is it seems they're not too worried about pandering to new viewers. Either you knew what was going on or you're not gonna watch the show again. Which is how it should be, being the 5th season and all.