Google added Google+ Circles integration into Google Voice today, which means you can now have customizable phone actions based on what circles you've put people into.
While you could previously assign groups to perform certain Google Voice actions such as going straight to voicemail, call screening, custom voicemail greetings, you can now add people using circles who you may not even have as a phone contact in the first place.
This can be useful if you have creepers in your circles who you don't want contacting you, or if you want to set up a custom voicemail greeting for all the Google+ contacts who just got your phone number from an ex. Alternately, for those who want call screening, but not for friends or work, you can configure that as well straight from your Plus page.
While not game changing, the integration of the Google+ social network into how our phone operates as a phone is yet another step the company has taken to become one giant communication thing.[Google Blog]