Push use of Circles across all Google products; I want the
  ability to share a Google Doc to all in my ‘Colleagues’
  circle, share a Calendar Appointments to all in my
  ‘Friends’ circle or send a text message from my Android
  handset to all in my ‘Family’ circle.  Circle integration
  throughout Google would be a killer feature.

This is the most important one in my opinion. Google+ has so much potential if integrated properly into the other Google products.