This is a huge first step to modern tv watching. I have DirecTV and Verizon FiOS internet, which is something like $200 per month. I am offered no bundled deals, so this is immensely appealing.
If they include local channels I would seriously consider giving this a try. I also hope it comes to Fire TV.
The other questions would be what about when you miss a show? Could you watch old episodes from the current season for free?
As someone who is in the process of cutting the cord (just ordered some gear, very excited!), I am hoping that the KODI(XBMC)/MythTV/etc community will work on something that integrates with this service as I can only imagine it will be a hot commodity when it comes out. It looks like they have already been working on a Xbox One app.
Local channels should be easy to get with an OTA antenna. If you live far away, you might have to put one on your roof. If you live within city limits, a simple wall-mounted, newer, "rabbit ears" style antenna should be plenty.
I'm thinking of building a hardware (USB TV tuner + Raspberry Pi) and software (Roku channel) solution that allows you to hook up an OTA antenna and stream it to any TV on your local network.
Right now we use our Roku box pretty heavily but have to switch to OTA to watch local stuff. Its a pain in the butt to have to switch TV inputs all the time and requires an extra remote control. An OTA Roku channel solves the problem of switching inputs and too many remotes. :)
Unless you really want to build your own, the HDHomeRun OTA box [1] will already do the above, and you simply have to plug it in to your local network.
If they include local channels I would seriously consider giving this a try. I also hope it comes to Fire TV.
The other questions would be what about when you miss a show? Could you watch old episodes from the current season for free?
UPDATE: Looks like a DVR like functionality is not available yet and you can only watch from one device at a time. http://techcrunch.com/2015/01/05/sling-tv/