Used epc.tmobile.com as my APN since day one.

Getting avg of 600k in Los Angeles.
Once, I get up to 1.2mbs in City of San Gabriel, CA.

Make sure you are on the t-mobile smart phone data plan, not Android.
Android plan will work, but not optimized. (I was getting only 200-400k, before the switch). Price is the same for switching.

Hope this help.