The lack of subscribers currently masks their poor spectrum holdings. If they were to really take off I don't see how the network could hold up under any sort of stress. With the small amounts of low band n71 and n29 for range, speeds would be barley usable at a distance. I think they only have 5 or 10 MHz of each in most markets. n70 and n66 can give you a few hundred megabits, but in highly crowded areas that may not cut it they get a huge influx of subscribers. and when on AT&T and T-Mobile, I would assume they are deprioritized.