Google+ for iPhone hit Apple's App Store a mere 24 hours ago but it's being downloaded like wildfire as it currently sitting atop the heap as the most popular free app available from iTunes. This is big news considering Google+ is still invitation-only and only has 18 million users] so far, compared to Facebook's 750 million. That said, Google+ users can now upload contacts from Outlook and Mac address books (not Facebook, though), which may result in even bigger Google+ adoption numbers.
Mobile Google+ early users are lauding features such as the app's push notifications for updates so when someone comments on one of your posts or sends you a message from a Huddle chat you can see it on your iPhone without having to open the app. The app's photo viewer also includes an uploader that lets people grab shots from their phone's camera.
Some features from the desktop Google+ don't yet translate to the app experience. CNET's Josh Lowensohn] points out that "there's no video chat option to make use of the multiuser video hangouts feature, even if you're on an iPhone 4 with dual cameras. Also, the Circles organizing is just a big list of contacts, versus the drag-and-drop experience you'd get on the desktop. This makes organizing large groups of contacts more laborious but is understandable, given the smaller amount of screen real estate."
To download Google+ for iPhone, click here.