The bad thing about T-Mobiles LTE is that it very limited. There are only two areas near me that have LTE coverage and both of those areas are less than a mile wide. Luckily I live in one of those areas because AT&T has no LTE coverage where I live.
I notice that they're still filling in a lot of the announced markets. I get LTE inside a lot of buildings that previously were only 4G and also see less HSPA+ and more LTE in general now. Interesting though is that the download speeds I got on HSPA+ are still higher than the ones I get on LTE.