AT&T also has an option, called AIO Wireless. There are many other smaller players that are either T-Mobile or ATT MVNOs.
Also, does Straight Talk offer LTE as well? I think AIO comes with LTE. I also liked AIO's $70 plan as Straight Talk is limited to 2.5GB of 4G data on the unlimited plan.
(I use Straight Talk but was thinking about getting Nexus 5 which comes with LTE)
I'm planning to switch to ST when my AT&T contract expires.