Switched to N4 from my earlier phone which was a Moto Atrix 2, so that was non-LTE as well. Had to go and get a new MicroSIM from the ATT store, but being a corporate store and not an authorized reseller, I got the new MicroSIM for free (authorized retailers charge upto $25 for that). When you get the MicroSIM, pop it into your N4, and hopefully you should be good to go OOTB. I have been reading that some people do face issues, and need to call up ATT to solve them, but luckily that wasn't the case with me. AFA the speeds go, I am getting decent speeds with HSPA+, a notch better than my earlier phone, but I never was an LTE user to begin with, so not really sad about not having LTE now either