http://www.macnn.com/articles/12/01/31/invites.no.longer.equired/
Valve opens up Steam Mobile beta to general public
updated 04:35 pm EST, Tue January 31, 2012
Invites no longer equired
After a brief period of exclusivity, Valve has opened up the Steam Mobile beta to the general public. Previously just a select group of Steam users were allowed to try the beta, although invites handed out to testers gradually increased the userbase. Free Android and iPhone versions of the mobile client are available.
While people can't actually play games using Steam Mobile, they can keep track of friends on Steam, chat with them, and access news, groups, and user profiles. The apps also allow buying games, which can be downloaded once a person is back at a Mac or Windows PC.
Fresh-Faced Recruit
Joined: Oct 2009
It's an excellent app
I've been using it since the second day it came out (I was invited into the beta very quickly), and it handles and feels just like a regular iPhone app. I'm really liking the chat features (though two criticisms: no slide down to hide keyboard like in Messages, and the text does not scroll up when you open up the keyboard either in portrait or landscape mode), and for what it was meant to do, it's an excellent app and addition to the Steam service.
One feature request, though: Steam Trading (and Inventory). If the mobile app had Steam trading it would be the ultimate mobile counterpart for any PC gamer.