morciu: well there is no mouse look and you have to have both your hands on the keyboard doing movement and camera rotation. It's not unplayable, it's ok I guess, I played it like that back when it came out.
You must have both hands on controller as well. I have my keys configured so I have camera controls and movement keys next to each other. No problems there.
morciu: Recently I decided to use my gamepad and honestly there is no comparison. You can just sit back with your feet on the desk and with the controller comfortably in your hands and enjoy. You can use everything even the analogue sticks.
If you don't have a cheap gamepad around then keyboard is ok but there is no reason to not use the gamepad if you do.
As I mentioned, I do have a gamepad (two actually), and it works better for Defiance. I tried using it with SR1, but I saw no advantages and switched back to keyboard after an hour.
morciu: A lot of games like this are made specifically for the gamepad and the pc ports didn't receive too much attention when it came to controlling the game. They just remapped the gamepad buttons on a keyboard and let you make the best of it.
In most cases where the game offers actual mouse controls I find it almost always better to use M&K. And usually controlling the camera is done with the right analog stick, which means you either control the camera or the 4 control buttons.