Good.  
Collections is the best feature of Google+ and a way better implementation of the circle feature.  
Communities is another strong point of the service, even though Collections alone would have been enough for me.<p>The mobile design on Android is disconcerting to say the least, according to the material spec, tabs are at the top.  Putting them at the bottom allows one handed navigation BUT is way too close to the navigation bar and usually cause many false taps.