I just got it a few weeks ago, and boy howdy is there a learning curve. Here's what my experience has been; yours may differ because of the market you're in.
NBC: It's included. I can watch and record and any all NBC content, like The Tonight Show, Saturday Night Live, and so on. I can fast-forward, rewind, etc. The local affiliate is... not mine. I don't know where it is, since I fast-forward through commercials and don't watch local news. But I've caught the tail end of a weather forecast and there appears to be an ocean on the map, and I'm a thousand miles from the ocean.
FOX: Same as NBC.
ABC: Not included on Sling, but is included with the Roku, for free. I don't think I can watch live TV, but there's nothing on ABC I care to watch live, so there it is. I can watch any and all ABC content that's available to the general public on ABC(dot)com. Can't fast-forward through commercials.
CBS: Not included on Sling, it's there on the Roku, but you have to pay for it. CBS All Access is $5.99/month for "limited" commercials, $9.99 for free. I'd have told CBS to go screw themselves but for the fact that some of our favorite shows are on CBS. We pay for the "limited" commercials, so we can't fast-forward. We can watch live, and the affiliate is actually our local affiliate, go figure.
I hope the FCC, the networks, and Sling figure something out so Sling users can get the networks without having to pay extra or go through all this hullabaloo.