I've been watching Sling for several days now on Roku (and finally cut the cord). I have to say that it does give me the cable fix - at least what I need. Travel, Food, Home Buying, Home Reno - a bit junky - but I used to mostly watch these on cable as well. Besides other reality shows based on Alaska, Moonshining, etc. that I used to watch and now wish Sling would play them as well

The quality is really good, and it almost works like a DVR, i.e. one can pause (but not really record, but I think it allows us to watch older shows as late as 48hrs ago on demand).
I've actually been using Dish World on Roku for foreign language content, and Sling is copied from Dish World. In fact, when I launched Sling, it actually first logged me in with my existing Dish World account (and I had to reset my Sling password, logout from Sling, and log in with my Sling account).
Not sure if I need this junky fix for $20 a month. Interestingly, even though I watch a fair bit of sports, I haven't really bothered watching ESPN or ESPN3. But maybe it is just me.
I also have Mohu Leaf antenna with ChannelMaster+ DVR for OTA channels, but it has been a bit flaky. When watching a recording (Elementary), quite often, there will be bad patches. Maybe it is the bad weather in Chicago - I don't know. But I do wish that Sling could have added these OTA channels - to me, that would have made their offering even more compelling.
As far as the money itself is concerned, I'm happy about one thing. At least they don't do the bundling thing that Comcast used to do - and at least I am on control of what I am watching and how much I am paying. But still - I think this is worth $10 not $20 - as it stands. Also because most of this content is available on Hulu or Netflix anyway, to which I already subscribe. It's not like I really need to watch "breaking news" about Bizarre Foods in Madagascar.