I've tried SlingTV and www.directvnow.com. Directvnow is much smoother and you get more bang for your buck. SlingTV buffers too much and drops their signal too much. Directvnow offers 3 or 4 local channels now as well. I'd go with Directvnow.
USTVNOW is mainly used for service members and US citizens living overseas... I have never had a single issue with watching anything. You can even setup a FREE account that will allow you about 8 channels. I got it specifically to watch AMC and Walking Dead after cancelling cable. Most of the "streams" available online are spotty, especially on a popular show... USTVNOW was always available... clear... no lagging. Like I said above also, I can watch it from any device I have... iPhone, Android Phone, PC, Mac (There's a KODI add-on)... nearly anything with a browser.