My main phone is black Mi4 W 3GB/16GB and i won't change it before it breaks down (might even buy another one for backup if i see it for good price ). Hardware is fast enough for my use and i like f/1.8 aperture camera. It is also coolest looking phone ever made IMO. I bought white @ 9/2014 but upgraded to black in january 2015.
Mi4 3/64, since 9 months today runs marshmallow MIUI as a no Brainer. Not in a hurry to replace it as sd808 proc does not perform a lot better and faces heating issues and mi4c/'s are stuck in 5.1.1. Will see for a Mi5 next autumn if global rom is available.
Got it over 2 months now and very pleased with it. My first was a Hongmi, also great value for money but this one with 3gb is something else. One question though, why is the audio sound only working on the back camera and nt working on the frontcamera as well? Hope they will fix this in the future.