Im a 32 yr old male, and my hands are like a bunch of bananas... having said that i use this...
I own a single game that uses it... but own 20 games or so... and i use it... all the time...
Without it, after 30 minutes the hands hurt, cramped.
with it, its like holding my ps3 or 360 controller, its comfortable, ergonomic, ends the pain in your hands.
for games, i own kid icharus. and that 2nd circle pad made the game 1000x easier to play, without having to cradle the 3ds and stylus the screen
as a camera control (which sucked! dunno why nintendo ever thought that was a good idea).
My online team deathmatchs in that game actually got fun, i am no longer dying 5 to 1, but winning 2 to 1.
i would imagine any game using this is going to be leaps and bounds better, and i have to now get a 2nd one for my blue 3DS XL.