I have always wondered how come RIM doesn't have us test out more OSes through the Beta Zone. It's probably because that's what carrier testing is for but some reason, every once in a while a T-Mobile USA OS shows up in the Beta Zone. We've seen this as far back as the Curve 8900 and as a recent as the Bold 9900. This time though T-Mobile USA is launching a whole In-Market Beta Program for the new 7.1 OS through the Beta Zone. If you are a T-Mobile subscriber and are rocking an OS 7 device, head on over to the Beta Zone and sign up! Then come back here and share with us what you thought of the upgrade.