If you check out the landing page for the service at lifestream.aim.com, you'll be able to update and monitor your posts and pictures on Delicious, Digg, YouTube, Flickr, Facebook, and Twitter alongside your AIM status (and with your AIM buddies in the mix). The Mac and Windows clients for the service are expected on 9/22; it's not known yet when the Lifestream goodness will make its way to the free & ad-supported AIM client for iPhone.
Although you can certainly handle multiple social services from several Mac apps (EventBox, Tweetdeck, MoodBlast), and the iPhone has multi-chat tools like Nimbuzz and Beejive, having the flow of statuses pouring in for AIM users will up the ante considerably. We'll keep an eye out for the official Lifestream launch next week.
Forgot to mention: Can we please, please have an AIM client for iPhone that supports group chat? If we're going to pony up $2.99 for the premium AOL client or even more for Beejive, it should have this bit of functionality, don't you think?
Note: AOL is the parent company of Weblogs, Inc. and TUAW.