Finally got to watch it after hearing some good stuff, and wasn't disappointed. Good humour full of pop culture references that aren't forced in the slightest. It all makes sense. Like Little Rock schooling Tallahassee on Hannah Montana, etc. I was expecting it to be more action, with comedy mixed in, but it seems to be a comedy first, as most of the action and violence is played for the highest comedic value also.
I liked Donnie Darko, and even enjoyed Southland Tales, so it's no surprise I enjoyed this. It's hard to talk about though, without giving too much away, because the conceit of the button and the random death plus a million dollars is only a very small part of the puzzle.
Since it is based on a short story, it's also heavy on morality and irony. The only thing it's not heavy on is details. You have to fill in a lot yourself about what's going on.