The Circle Pad Pro isn't too pretty to look at with its irregular shape, this being due to the designers having to work around access to the volume slider and earphone and charging sockets. To the rear of the controller there is an infra red transceiver which covers slightly less than half the controller's length and which blocks access to the stylus and cartridge slot. Overall the appearance is of something that has been botched together to fit around a device which wasn't initially intended to have such an attachment made for it. The asymmetry between the screens and circle pads doesn't look too nice though I find it doesn't affect game control.
The Control Pad Pro's battery compartment is fairly easy to open, it has a big wide screw head which can be undone with a coin so there is no need to hunt for one of those little Phillips screwdrivers that fall out of crackers.
It is much lighter than the 3DS though it does add weight as well as bulk and has been ergonomically designed with contours which I find comfortable to hold, it feels a little like holding an Xbox 360 controller, though without the handles resting in the palms.
There are three shoulder buttons on the controller, a R button above the right circle pad which functions the same as the one on the 3DS, this has been included to prevent an uncomfortable stretch to the 3DS's R button. In addition there are two extra shoulder buttons, ZL and ZR, and they are more comfortable to reach and use with the two circle pads than with the L and R buttons. The right circle pad feels to be the same quality as the 3DS's left pad and moves equally as smooth.
There is no on/off switch, the unit switches itself off after 5 minutes of inactivity.
So far Resident Evil: Revelations is the only game that supports the Circle Pad Pro. The game plays great without the Circle Pad Pro but I prefer to play with it attached. To move while aiming with the default 3DS button configuration you have to press the left and right buttons together with the left circle pad but with the Pro you only need to press the ZL button with the left circle pad. To aim you press ZL and ZR to shoot, I find this preferable to pressing the R button and Y to shoot. I don't think there is much you can do with the Pro in this game that you can't do with the 3DS buttons though with the Pro you can move forwards, backwards, left, and right with the left circle pad while at the same time adjusting view and turning with the right circle pad. After playing with and without it I prefer to play Resident Evil with the Circle Pad Pro because it feels more intuitive and just adds that little extra dimension to the gameplay.