For two hours the movie is reasonably diverting, but not particularly memorable; thing is, the movie goes on for another eight minutes before the credits, and those last eight minutes are really something. See, the film suddenly moves from... the best way I can think of to describe it is a move from the indicative mood to the subjunctive. For a last few moments, the protagonist has more than one possible life ahead of him, and if he made the risky choice... and everything went impossibly well... It's a bit like the one e-sheep comic I really liked, The Guy I Almost Was. In fact, while I originally ended that last sentence with "except in this case it's an extended coda and not the heart of the story," it suddenly occurs to me that, duh, it is the heart of the story. That's the 25th hour of the title. And it by itself makes the film worth watching.
Weird endings are neat. By this I don't mean twist endings — gasp! the killer was actually HIM! whoa! — but abrupt changes of perspective. I thought AI was massively improved by its millennia-later final act, and Mulholland Dr. by its dive into the box. Sure, they can get gimmicky, but they certainly beat just petering out, like this article.