Google+ update adds Hangouts from Messenger
As for the real guts of this update, which brings Google+ to version 2.3, the changes focus on photo UI and Messenger. The changes in photos make the UI fit a lot better with the new higher-res images that you'll see throughout Ice Cream Sandwich. The photo tab now shows large extrawide images for each album, similar to the contact images in the People app. There is also a new icon to show which pictures have been uploaded to Google+ with the Instant Upload feature.
The bigger changes come in the Messenger app, which now has the ability to leave one-to-one conversations and has people suggestions when composing a message. But, the biggest addition is the ability to start a Hangout from a Messenger conversation. This marks the first time that users can start a Hangout from the mobile app. Previously, users could only join existing Hangouts.