Ok. I love this show, and thought to pop in and give my thoughts on the latest episodes.
So some spoilers may be given.
DAVE is the most standalone episode this show has ever had. I think the writers gave us a few interesting character reveals, but most of this episode was about messing with the fans.
They obviously toyed with us about the Island being all a dream, a previous theory...and about the Island being Purgatory. Henry's rant to Locke "Do you think God can see us here?" or something like that.
Finally I believe they are messing with us about the theory of the button. Either one of two things is happening with the button.
1)The button isn't real and it is a psychology experiment. That would mean that somehow the survivors found the one of the least important hatches on the island, and the experiments going on/ or WERE going on with the other hatches are all more important. I really can't get into this theory, though if its true it would fit with the mind games that Lost writers are giving us. (Best mind games since X-Files by the way.)
2) The Button and hatch DO something. We just don't know what yet. Henry could be lying to Locke and he really has pushed the button. Locke's character theme is that he is looking for a friend or family that he can trust, and he is gulliable and can't let things go. Perhaps Henry has gotten to him by staying and saving his life. And now Henry has an ally to manipulate. Remember, he wouldn't have suspected that Sayid would have dug up the grave...who would defile a grave?
The second option is that Henry didn't push the button and it STILL does something or is in the process of doing something and we don't know what it is. This is personally what I believe...and I say we may or may not ever find out if this is true or not.
But too many wierd things are going on with the Island for this one experiment to be as simple as a test to see if a 2 man human team would continue to push a button indefinately. Humans thrive for a purpose in life, and I have no doubt that given the right circumstances that someone told to push a button would create that as their purpose.
Of course...if there is no purpose to it...like Jack said at the end of Season one. We are about to have a Locke problem. And this Locke problem is going to be very big, and very dangerous.