I grew up with Wolf3D, Doom, Duke Nukem etc, so I was an arrow keys user. WADS was like a god send, I even saw people playing Quake with a joystick in the interim. Remember holding Alt to strafe, people?
OT: Since I've been using it since I was a young fella, I've grown very used to it. But very recently, I've run into a problem with it. F3AR. See, I usually use Space to jump, except for cover-based games where Space is to take cover, or vault over it, or whatever. However F3AR has a jump and a cover button. And I use a Razer keybaord, which actually makes it a bit of a ***** to use your thumb to hit Alt, and my lil finger is for holding down Crouch as well (I don't like toggle crouch, makes it awkward to poke in and out of cover swiftly to pick off shots).
I ended up mapping "cover" to C, because it's like a toggle cover, not a hold down cover. So that worked out in the end. But yeah, other than that, no problems whatsoever. Although those gaming pads in this thread look pretty boss, might try one out.