I talked to T-Mobile and they said that if you purchase a phone & plan there is a 30-day money back guarantee. So if you get home and your coverage is sub-par then you can just return everything for a full refund, no questions asked.
I am also seeing miscellaneous reports that T-Mobile claims to have HSPA+ in Phoenix, however they actually do not have it. I cannot confirm or deny the truth in this statement but keep it in mind when you go to test the phones at the T-Mobile stores.
Note that thoughts expressed here are merely my personal opinions and will hopefully "There are in fact two things, science and opinion; the former begets knowledge, the latter ignorance." ~ Hippocrates
"If anyone's head is acting an antenna, seek help or wear tin foil." ~ EarlyMon
share my thoughts on the matter to stimulate a respectful discussion.