to those having Frame Rate issues on the PC:
Vsync: off
Framerate: unlimited
Then go to My Documents and open the engine config file (back it up first!):
C:\Users\*username*\Documents\My Games\Borderlands 2\WillowGame\Config\WillowEngine.ini
Search for
MinDesiredFrameRate=35.000000
change it to
MinDesiredFrameRate=60.000000
Before that my fps bounced from 30 to 60 (exactly) depending on which way I was facing. Now it never goes below about 55 (facing the direction that used to get down to 30).