Messages to replace iChat in OS X Mountain Lion, public beta available today (Updated)
Apple on Thursday released a public beta of Messages, its next-generation messaging app for the Mac that will be a part of Mac OS X Mountain Lion. It lets you send and receive iMessages, just like iOS devices running iOS 5. Now you can "text" chat via iMessage with the iPhones, iPads and iPod touches in your life.
Note that when installed, Messages replaces iChat, but not its functionality. You'll still have chat support for your AIM, Yahoo!, Google Talk, and Jabber accounts. As with iOS, Messages lets you see when your partner is typing via an ellipsis animation. Messages also supports drag-and-drop support for sharing photos and videos.
This is a beta build, so expect changes before the final version is released. Lion users can try it out. Note that it requires Mac OS 10.7.3. Have fun!
Update: The beta release seems to be temporarily unavailable. Apple notes: "Our apologies but there was an unexpected error with the application. This problem has been noted, and an email has been sent to the administrators. Please check back in a few hours to try the download again."
Update 2: It's back. You will have to reboot after installing.