Basically, the carrier is aiming to double its speed every year, until they reach 672Mbps, which is the theoretical maximum that the technology will be able to squeeze at this point. Issues with the perceived latency compared to Verizon's LTE were also addressed by downloading a music album from Amazon, and playing a car racing game in an online multiplayer session over the 42Mbps network with little to no lag.
As per T-Mobile, in the last few days it has been running tests in Las Vegas among Verizon's LTE, HSPA+ and Sprint's WiMAX, and found Verizon's LTE only marginally better, both in terms of speed and latency, while Sprint's 4G had been way behind. Such tests have to be taken with a grain of salt, though - despite being real life, they thoroughly depend on the location and the coverage, so your mileage can and will vary. T-Mobile wrapped it up by announcing the Dell Streak 7, while the T-Mobile G-Slate was held briefly in the beginning of the press conference by both LG and T-Mobile's CEOs.
The take from T-Mobile's presser was that there will be bread and butter in HSPA+ for at least the next 5 years, so that's what they will stick with, and current 3G device owners will also benefit from increased speeds.