Starting September 12 (the same day the next generation iPhone will be announced), T-Mobile retail staff will begin training on setting up an iPhone for customers, and each store will have a 4S demo unite on hand. The carrier is also working on iOS versions of their current mobile apps, including T-Mobile myAccount, T-Mobile Visual Voicemail, and T-Mobile TV, which will eventually be available on the AppStore.
Customers with an unlocked iPhone on T-Mobile are stuck with 2G EDGE service, unless they are in an area with HSPA+ 1900. T-Mobile is still working on rolling out 1900mhz frequency to more areas, but it is still limited compared to its entire 3G/4G network.
Customers on T-Mobile do have access to the new "truly unlimited" data plan that was just launched last week. Since AT&T and Verizon no longer offer unlimited data plans, Sprint and T-Mobile became the sole providers of this service.
The iPhone has caused the subscriber loss for T-Mobile seen in recent quarters, but perhaps these new measure will help them win over some unlocked iPhone users, as well as their new plan of "Selling Against the iPhone"