Instead of posting these findings as comments on other posts, I'm going to start a new topic. Here you go.
It's an unremarkable device. It's huge, and it really does feel as cheap as it looks.
The Sling integration appears to be a Sling TV logo in the upper right hand corner of the home screen, a special Sling TV app and on startup Sling TV launches.
This is certainly not as slow as the Nexus Player, and I'd say it is on par with the Mi Box, maybe a bit snappier. I've only been using it for about 2 hours.
I'm not sorry I bought it and I'll be keeping it. I won't be buying another.
Edit: I got downvoted for sharing observations on a new device? Fuck you guys.
More info -
There's some fuckery going on with the Live Channels app, as in, the app doesn't show up when there are compatible apps installed. I look into that more over the weekend.
Netflix listing are included in the Sling app. There's a Netflix row in the My TV tab.
The Guide, Sling and Heart buttons on the remote take you into the the Sling app.