Editors' note: This post was updated July 16, 2013, with more information.
Having the app on your home screen gives you immediate access to one-on-one and group video calls formerly found by going through a couple of menus in Google+. With Hangouts, you can have a video call with up to 10 people and you can choose who will be in the hangout through a list of your contacts or by using a search field. During your hangout, the app automatically detects and displays the person who is currently talking, with smaller live shots of the other people in the hangout across the bottom. You also have buttons across the bottom that let you switch between your front- and rear-facing cameras, turn off the camera or microphone, and quit the hangout.
But the Hangouts app isn't all about video calling. As the replacement to Google Talk, Hangouts is now the go-to app for chatting with your Google contacts. It lets you start conversations with individuals, groups, or even entire Circles. As you chat, you can embed emoji or attach photos (new ones or existing ones from Google+ or your Gallery) to a message. And with a single tap, you can instantly jump into a video call from a conversation. My biggest complaint is that unlike Google Talk, the Hangouts app doesn't show you which of your friends are currently online. While Hangouts on the Web displays status messages and color-coded status indicators next to your contacts, the mobile app displays neither, which is frustrating.