I got this phone last weekend. First impressions are good. Coming from a 635 which was my first Windows phone. This is my first unlocked phone of any kind. I miss WiFi calling.
libra89 is correct. Only non-branded iPhone running iOS 8 or higher can get WiFi on T-Mo as a BYOD. All Android, WP, BB, etc. must be branded to get WiFi calling on T-Mo.