Taken from
HTC One Developer Edition Is a Bogus Unlocked Phone | News & Opinion | PCMag.com
Here's the problem: the Developer Edition has HSPA/WCDMA 850/1900/2100 and LTE 700/850/AWS/1900. If you don't know what that means but you're still cheering for unlocked phones, you need to get educated fast, because this is the problem with unlocked phones in the U.S.
This phone will only work properly on AT&T.
On T-Mobile, it will get 3G in some cities, but not in others; it'll be stuck on 2G in many places. It might get LTE in the future, but we're not sure. Ditto for Simple Mobile, Ready SIM, Straight Talk, and any other carrier that uses T-Mobile's network.
It absolutely won't work on Sprint or Verizon, Virgin or Boost, MetroPCS, Page Plus, Clearwire, PlatinumTel or any other carrier that uses the Sprint or Verizon networks.
there you have it!