T-Mobile IMHO is by far the most open of all the networks in the US. The only thing is their 3g network isn't that widespread yet. Verizon Wireless blows because of their locked down network even though they provide the most 3g coverage, and ATT's 3g has such high latency.
really makes me wonder where tmo will be in 5-10 years. how much more growth they have. if this kind of stuff keep sup they have a lot of potential. -- sbcglobal.net speedtest result 11/11/09 - 5256kbps