Summary: Very disappointing. Build quality is questionable, it doesn't work with a lot of games and their 'app' is a broken mess.
1. The device is VERY small. I have small hands and it is difficult to press the L1, R1, L2 and R2 buttons because the thing is so small. Some one with slightly larger hands would probably have a really hard time using this device. This isn't a knock per se, because it is advertised as a 'portable' solution. You just probably don't want to plan to do any extended gaming on this.
2. The build quality feels light, cheap and 'plasticky'. I feel like I am going to break the L2 and R2 buttons every time I press them. This feels like a cheap $15 knock off controller, not a $40 controller in the same price range as an XBox controller.
3. The analog controls are stiff and imprecise. They are not covered in the same rubber texture that the body is covered in, and the raised 'bumps' that are there to provide grip are VERY raised. It feels like pressing your thumbs on tiny spikes and is not comfortable.
4. The free app that exists to allow you to map buttons (which would solve the game compatibility problem) does not work. The entry in the Google Play store warns the app 'is in beta'. 'Beta' is being generous. I could not get the app to sync the controller on either my HTC phone or my Asus Infinity. The sync process crashes at 50%.
Even more strange is the fact that the app doesn't use the 'App Mode' of the controller. When starting the app, a warning appears that 'In the current version, the app uses the HID/Game Pad mode'. The 'App Switch' at the top of the controller has to be in HID/Game pad mode to work (it still doesn't sync even when you use the right mode).
I am not the only one with this problem. There are numerous complaints and '1' ratings.
5. Unless your game supports this pad specifically or has built in remap functions, the controller is probably not going to work. In Snesoid for example, only one of the analog controllers and the 'Y' button work, and the rest just cause the 'Exit App' screen to appear.
6. The charging dongle that comes with the controller is an actual dongle. It is not a cable. This makes it very difficult to charge the device.
Conclusions. Right now this was a waste of my $40. When the app is fixed the pad might be usable, but it still will not be a product I would recommend to anyone.