Generally a nice app. What I was missing was a way to set the user globally on all sites. Instead you have to set the active user for all the sites. I don't see the usefulness in being able to set different users on different sites...
The best way would be to be able to log in, but you commented elsewhere that this is not yet supported by the API. I would see this to be the first priority when (if) it does! 

I also noticed that YouTube links in the "Musical Practice & Performance" site were replaced with large placeholders for the video, but no video. See [this answer][1].


  [1]: http://music.stackexchange.com/q/4648/249