The final part of the Metro Last Light E3 demo is up (gosh, they made this one last, didn't they?). You can see part one here, and part two here. This third part contains the action bit, an on-rails minecart shoot-out that I think demonstrates the engine at its absolute finest. Incredible lighting and cloth physics give this an air of realism that's a little nerve-racking. You can see it below.
The game is due out at some point next year.