A little surprised by the pretty plastic side of the assembly. Then we go to serious business, the quality of the display, the camera, autonomy, and especially the dual Sim is a real pleasure with the Windows system. Finally the weight, I who also Lumia 830, I am very surprised at the lightness of the 640 XL. For dual SIM management a priori, subject to error, the DATA is set to one of two SIM. It is therefore not possible to specify an application to use a Data SIM 1 and another of the DATA SIM2. In my case it is a bit annoying because of my professional Data SIM1 does not support MMS and even if I configure sending SMS to the contact on the SIM2, the data necessary for the MMS through SIM1. So the MMS is rejected. This is a detail somewhat unusual in my case, but nothing more annoying.
