I just happily bought this in the Steam Summer Sale! Yay me! oh wait, game stutters like a son of a bitch and is impossible to play. Spend an hour going through a multitude of settings from bare minimum to maxed out. Nothing changed the problem, I will try disconnecting my tethered SGS3. Kind of a pain in the ass and they should be able to fix this problem..
EDIT: Sure enough, disconnect my Samsung S3 and Boarderlands plays smooth as butter, sad they have done nothing in all this time to fix this bug..