T-Mobile's "Un-carrier" strategy of offering unlimited data at cheaper rates had the impact of slowing down the networks of their competitors Verizon and AT&T. The Techspot article entitled, "Verizon speeds slowed after unlimited plans introduced", explains the situation further. It also appears that T-Mobile speeds were generally faster than Verizon's. Additional resources can be found here:
T-Mobile Beats Verizon in Tests, Availability (Android Headlines)
And for a broad view of the State of Mobile Networks, go here.
What is T-Mobile's plan with offering unlimited data?
The author of the Techspot article captures the big picture:
What else is T-Mobile up to?
T-Mobile to finish new store at Showcase Mall on Las Vegas Strip (Las Vegas Review Journal)
T-Mobile hiring 170 employees as it opens 24 retail stores in Arizona (Phoenix Business Journal)
T-Mobile will no longer support its Windows app by end of August (Digital Trends)
T-Mobile May Enter A Merger Based On Synergies, Deutsches Telekom says (Android Headlines)