Unlocked AT&T HTC One M8 on T-Mobile?

[The J]

Hey all,

The USB port on my T-Mobile HTC One M7 is failing, so I figure that's a good excuse for an upgrade. :thumbsup:

I'm considering purchasing a refurbished HTC One M8 Windows, but ones I can find are for AT&T (here and here, for example). The AT&T version seems to support T-Mobile frequencies (see here), so is that all I need and it'll just work with my T-Mobile SIM? I assume that I'll lose out on T-Mobile's Wi-Fi Calling feature (unless I can install it separately)?

Edit: Actually this app might work for Wi-Fi calling? Anyone successfully install it?

Also, does anyone know how well Windows Phone works with Ford Sync/MyFordTouch? I assume it'll be fine, but I might as well confirm.

Thanks!