PC Mag has posted a review of 521 -
Nokia Lumia 521 (T-Mobile) Review & Rating | PCMag.com
"The Lumia 521 can hit up to HSPA+ 21 speeds on T-Mobile's network. It's a little disappointing that it doesn't support the carrier's faster HSPA+ 42 or LTE networks, but it still managed to pull in some good data speeds, with an average of 5.4Mbps down and 1.5Mbps up. It also supports 802.11 b/g/n Wi-Fi and Wi-Fi calling."
My Speed Test Say Otherwise
Nokia Lumia 521 (T-Mobile) Review & Rating | PCMag.com
"The Lumia 521 can hit up to HSPA+ 21 speeds on T-Mobile's network. It's a little disappointing that it doesn't support the carrier's faster HSPA+ 42 or LTE networks, but it still managed to pull in some good data speeds, with an average of 5.4Mbps down and 1.5Mbps up. It also supports 802.11 b/g/n Wi-Fi and Wi-Fi calling."
My Speed Test Say Otherwise