According to TMONews, T-Mobile will start offering additional support to its million customers that use unlocked iPhones on their network. There's a screenshot of the leaked document above.
Basically they are going to have more iPhone specific information for their customers and customer support to help iPhone users. They are also asking their reps to read up and learn the information to be more helpful.
Also it has been rumored that the next iPhone will expand it's frequency range to be able to offer 3G to other carriers such as T-Mobile. Currently T-Mobile users can only access the EDGE network.
I'm on an unofficial carrier (not T-Mobile) and I am listed as having an "other" smartphone. There's no documentation or support on my carrier's site. When I've had to deal with their support it's been mostly for billing changes and I've never had them help, or offer help, or even ask what phone I have.
Anyone here on T-Mobile have any success or assistance from them regarding your iPhone?