I just signed up for Sling TV's 7-day trial. It was easy. The app works on Mac, iPhone and iPad. Picture and sound are cable quality. Sling TV works.
Apparently, simultaneous viewing of Sling TV on multiple devices is not yet supported.
While CNN shows commercials, ESPN/2 do not, electing instead to post a logo billboard with a music bed, for the duration of the break.
What's missing? The ability to use Sling TV to watch only, the networks of your choice (i.e. Viewer's Choice).
Check it out, though. It does offer a tantalizing glimpse of how things could be, for the TV viewer. My grade for Sling TV = B:
Here's CNET's more detailed review:
http://www.cnet.com/products/sling-tv/