Not gonna lie when I was heavily into FPS games on PC KBD and mouse every time trumps a controller. For aggressive mobas same situation. For everything else though why not lean back and relax with a wireless remote in your hands???
Seriously though the steam controller is beyond cool. I was actually using it to browse the web earlier. Given it was kinda slow it was still easy and relaxing. The configurability of it makes it super handy, but I did do something similar with my XBOX remotes using XPADDER and was able to do wayyy too many things not designed for a gamepad with one. Still the included features are neat, and I look forward to using it for a long time. Nonetheless there are some games where a true dual joystick pad just cant be beat.