I received the Oppo R9 mobile phone today. I bought it as it allowed me to install 2 SIM cards (for my Singapore and Indonesian cards).
It was quite easy to install the SIM cards and to set up the phone to use. The features were well designed. I did not have any trouble in getting use to this new phone.
My earlier phones were Samsung and HTC. I had a lot of trouble with these phones. The Oppo was easy. Maybe, I have become more experienced with using mobile phones. Maybe their user interface is better.
My report on Oppo - Excellent!