In this day and age, you'd think it would be the standard across every game, to allow you to customize controls however you want them on the PC. That's usually the joys of playing on PC, the lack of such restrictions. It drives me nuts when a developer doesn't do this.
For instance, I almost bought Magicka the other day. Well, I decided, I should probably get the demo first, just in case. Good thing I did. My middle mouse button is apparently no more. Not a problem, I usually think, as there are a great many other buttons on my mouse to use instead, and it always feels kinda awkward using the middle one. Whelp, turns out you can't actually rebind the cast spell key to anything but the middle mouse button. As a result of not allowing me to customize my controls, they lost a sale.
Take a note, developers. This not only makes a difference for disabled gamers, but also for those of us who have certain standards we try to maintain with our control scheme.