Hi There, T-Mobile.
Hate to be a nag/broken record, but, in case it's fallen through the cracks...
Please, please, please do whatever you must to work with Google to Find A Way such that you can add WiFi calling to T-Mobile customers' devices when they own handsets with "vanilla" Android, such as Motorola Moto X/G and Nexus devices. I'm an ex-senior software developer, so I know smart, motivated people can find a way.
Eventually, the HTC Sensation 4Gs my wife and I have on your network will need replacement. I am disinclined to buy new handsets riddled with bloatware that makes them slow, laggy and inconsistent. (E.g.: Tap something on the screen and wait. Is it just being slow, or did it not register the tap?) But we also require WiFi calling. TMO is marginal in our home (tho it's supposed to be solid) and we travel to places where, quite frankly, TMO has no coverage.
Please do not put us in the position of having to decide between usable handsets and T-Mobile. We like you. We want to stay with you. But that won't overcome the need for usable handsets on a usable network.
Thanks for your consideration of my plea,
Jim