In general, the Mac app works great for me. I just have basic cable so I don't need HD. The things I like about the Mac app:
The small picture in the corner of the screen.
The ability to make the picture whatever size I want
The ease of making shortcuts.
The remote is easy to use.
To me it looks like Sling will abandon the Mac app and concentrate on the web app. If not, you need to reassure Mac users that a new version with HD support is coming. I have a separate post on the web app.