I was also thinking about buying Dark Athena seeing it's at a shocking price of 3$, however I've played both Butcher and Athena.

So, how long is this game going to last me, what level of quality is there, does it get repetitive? Is it open world? Does it support a gamepad (also, does Riddick support a gamepad)?

Just buy the damn thing. And no it is not open world.

Alan Wake?
EDIT:
Oh, yeah you mean Alan Wake (duh!). Nevermind.

I'm thinking about going to bed, that's what I think.

This++

It's a decent game with an interesting story and the DLC is actually pretty good as well.
It does get repetitive quite quickly, but not in such a terrible way as to make you want to uninstall the game. If you like horror stories and action adventures you should get it, especially at these prices. Just don't expect more out of it than it is, it is just a linear game that tells a decent story and provides several hours of fun. (even without the DLC)

I played through most of it in one sitting a few years ago; I really enjoyed it, it's hardly groundbreaking or worthy of histrionic praise, but it gave off an innaresting atmosphere, gameplay was smooth and the songs coming in at the end of each chapter is crazy effective.

Probably because I'm a Nick Cave fan.

Buy it for the absolutely gorgeous environments and the dark, foreboding tone that permeates the entire game. The setting for the game is fantastic, and feels very alive and real. No, it's not open world, but there is some ability to explore the levels. And it can get repetitive if playing for a long time, but as the game is split up into "episodes", playing just one at a time helps alleviate that. The gameplay (with the DLC episodes) is about 11-12 hours, and I personally think the story is quite strong. Definitely one of the best games I played this year.