Personally i dont go over 90 for FOV.One thing to keep in mind is that BC2 uses Vertical FOV and not horizontal. I start getting a fished eyed view above 90 Vertical FOV and yes it will demand more of your system because you are rendering more graphics
Here is a link to a FOV calculator that will allow you to type in what horizontal FOV you are wanting and calculated what Vertical FOV you need to get the desired Horizontal FOV .hope it helps
http://rjdown.co.uk/projects/bfbc2/fovcalculator.php