With 520,00 new subscribers, network launches in New York and Boston, and releasing their first Blackberry unit in 4Q of last year, MetroPCS certainly is on a nice run of late, you could say. So how did their first quarter go, you might ask? Even better than the last, adding 684,000 more subscribers. The only sore spot is all the customers they lost during the quarter.

Not all the news was rosy; their turnover rate was 5%, up from 4% last quarter. Only a high-priced phone binds them to Metro service and other carriers of prepaid cell phones, so Metro is sometimes seen as a temporary solution for cell phone needs. Even with a proprietary phone, some carriers now can flash your internals to work with their network, so their churn rate might always be a little higher than the norm.

MetroPCS now claims over 6 million customers in the US. This kind of subscriber explosion isn’t all that likely in the next 6 months or so; they did a little better by launching their services in new (and large) markets. Still, some experts are predicting they’ll hit 7+ million subscribers by the end of the year, which are figures most companies in their position would dream of.