Simple Review:

I gave one to my 8 year old daughter, who up till now did all her PC gaming with an XBOX 360 controller. Her initial response was, "It's kind of big".

We spent a day playing through all her favorite games (Castle Crashers, Dungeon Siege 3, Grow Home, Goat Simulator, and Risk of Rain) and no matter what kind of game it was she was able to play effortlessly with the Steam Controller. She even managed the 3D games better than what the dual analog sticks allowed her before.

At the end of it all she now prefers the Steam Controllers. I like them a lot, but I was worried they'd be too big of a jump (with the touchpads) for her but she needed no instruction and picked them up intuitively.

+1 to smart design that even an elementary school child can grasp and understand.