Okay, I'm finally caught up with all the posting since last night.
Things that still need to be addressed.
What the heck that key did. Here are my thoughts. It was said that an electromagnetic charge was building up behind the concrete barrier for 108 minutes, and that entering the numbers released enough of it to prevent it from going critical. Okay, so, if you think about it like encefilitis (spelling)... basically, swelling builds up in someone's brain, and poking a little hole in the skull relieves this problem. My guess is that what happened was that after the timer ran down, the swelling was approaching critical mass... and turning the key destroyed the concrete containment. Which is probably what caused the hatch door to go flying off... kind of like the popping of a champagne cork. I suspect that the hatch, while being worse for wear, will still be there and that Eko, Locke, and Desmond all survive. This is reinforced by the leak that Desmond is a full time cast member next season. The more I think about it, the more I think that turning the key did nothing more than popping the top off of the containment of the EM field.
Second major question. So, these scientist discover this electromagnetic anomoly, and contain it to study it. Every 108 minutes a little of the EM build up must be released. So, why not automate a system to do it? Why the heck have someone input a random string of numbers to release it? That doesn't make any sense to me.
And finally... a giant green talking condor. WTF?!?!?!
4 toes is pretty out there too.
I think I'm back to thinking that the island is Atlantis. It is also quite possible that it is in some sort of extradimensional area, outside of the real world. Otherwise, it would be easy to find, easy to get to, and easy to leave.
Bottom line, I had high expectations for this episode, and I feel like it lived up to them.