The biggest update of them all is that the iOS app now allows you to join Hangouts and be a part of the group video chat feature that has become one of, if not the killer feature of Google+. The feature is available on both WiFi or 3G and reportedly works well on both. We assume you'd need an
The update also brings granular control for notifications, allowing you to choose specifically what notifications you want to receive, rather than being inundated with info. It also adds ability to +1 comments, share posts with individuals and set your profile picture. And, adds improvements for +mentions and people searches.
The Google+ app is free in the iTunes App Store, and Google+ is open for all sign-ups if you aren't a member yet.
source: Anish Acharya