T-Mobile's network isn't the biggest, nor is it the best. I am a big T-Mobile fan and subscriber, but I will be the first to admit that it isn't perfect. But what I will say is that their service has improved greatly since I joined in November 2012. Now I live in an area of Detroit that is really close to Canada. In fact it's so close that Verizon doesn't have LTE or 3G, it's just 1x. Sprint has a tiny bit of 4G but not much, and AT&T has a few bars, but not much either. So I wasn't expecting much from T-Mobile when I switched. When I first joined T-Mobile, I was getting about 1-2 bars of HSPA+, which the speeds were around 10mbps at the time. This was before all the Uncarrier stuff started happening. Now, I am getting about 5 bars of signal and LTE that is about 10mbps still. The only network that is better is AT&T's, and the only real difference for me - at home - is the speed. So I said all of this to say that T-Mobile's network is improving. It's not the same as it was 5 years ago, or heck even 2 years ago.
NPD recently did a survey on wireless perception for all four carriers. They surveyed about 2,500 customers and T-Mobile tied for third place with Sprint at just 2% while AT&T was second at 10% and Verizon was first at 30%. It's not a very scientific survey at all, but it just shows the perception that people have towards T-Mobile. Which is why I was glad that they kicked off the Test Drive. So that people can go ahead and test drive T-Mobile's network without any money out of pocket. Legere has been up front about the fact that their network has not been the greatest, and that he and his team have been working tirelessly to improve that. And he wants to show that to everyone.
Here are some more interesting numbers from NPD's survey, as reported by Fierce Wireless:
"According to NPD's findings, around 52 percent of T-Mobile's own customers think that T-Mobile has the nation's best network coverage. But just 3 percent of AT&T customers think that T-Mobile offers the best network coverage. Around 3 percent of Sprint customers think that T-Mobile offers the nation's best network coverage, and just 2 percent of Verizon Wireless customers think that T-Mobile has the best network coverage."
I think this perception will change with time. But it's going to be the most difficult hurdle for them to overcome. And it'll be an even larger hurdle if they do merge with Sprint.