I followed the instructions here and it more than doubled my d'l and upload speeds. I'm on Virgin Mobile UK which uses the T Mobile network:
http://www.thegadgetmasters.com/2012/11/23/how-to-nexus-4-has-lte-how-to-enable-4g-lte-on-nexus-4/
Heres my speed:
http://www.thegadgetmasters.com/2012/11/23/how-to-nexus-4-has-lte-how-to-enable-4g-lte-on-nexus-4/
Heres my speed: