It might seem like an inconsequential thing, but like a number of people, I can't stand WASD keybinds and find myself rebinding keys for every single game I'm in. Please don't make it such a pain and ask me if I'm sure I want to rebind a key every time I choose to do so. Of course I want to rebind it, that's why I chose that option.
Secondly - you warn me about rebinding some keys that aren't shown as bound. I don't know if that's because they're supposedly hard coded or not, but it would be nice to not have it come up if it's a bug. I noticed this trying to rebind space when there was nothing else mapped to the key.
Finallly, mouse buttons. It doesn't fly with me that I should have to use the left and right mouse for what you want me to. I prefer to jump with the right mouse and aim with the thumb button. Do me a favour and expand the keybind interface.