Changing the game settings in the Console during the game disable Achievements for that session. What you do in the INI before you launch the game has no effect on those.
So... I'm completely unable to change the FOV to one that doesn't give me a headache and strained eyes, without disabling my achievements.
Bloody brilliant, the least that could be done is give PC users a FOV slider. Damned console port.
*Edit*
Unless there's a way of changing the FOV without the Console. Is there?