Got the Amazon Fire and signed up. Testing for a month before I cut the cable. So far so good, but i do have a very fast internet speed. I got the Fire because if you have the Fire or a playstation, you can see the guide that is similar to what you have on cable or satellite. I like that you can make different users with their own favorites on the guide.
You can log in multiple devices on Vue, but only one on Sling. That was the deal breaker for me with multiple TVs. They do have to be on the same ISP.
At this point I plan on cutting the cord at the end of the month and buying a playstaton later and putting the Fire on the bedroom TV.