Hi, I'm looking for some information on android usability. Specifically, I'm curious about how successful the basic navigation of android devices are using the back, option, home and search buttons. Some device manufacturers choose to modify the standard android navigation framework for their products and remove standard android buttons. I'm not sure if device manufacturers are doing this because they believe standard android is inadequate and they need to fix it or they are just looking for a way to differentiate. Unless there are serious usability concerns, It seems like it would be better to keep the standard android experience consistent from device to device. I'd really appreciate it if anyone could point me in the right direction of research in this area. Thanks.