Middle management. The Lumia 640 improves upon the predecessor in several areas. The middle-class smartphone features swappable covers and very decent software - but is that good enough to beat out the stiff competition?
http://www.notebookcheck.net/Microsoft-Lumia-640-Smartphone-Review.141607.0.html
The main problem with the Lumia 640 is that the nearly-identical 735 makes it hard to decide which to buy!
Maybe its just me, but that photo quality comparison the Lumia 640 looks far better than the other three do.