Phoneboy is where I first saw mention of Gizmo:
Hey look, it's Michael Robertson's attempt at cloning Skype: Project Gizmo. Since it basically is using the existing SIPphone infrastructure to pull it off, it's definitely SIP, it's definitely got connectivity with other SIP networks, and they've got inbound and outbound PSTN connectivity. PhoneBoy's Blog: Project Gizmo?
It's essentially a slick client for SIPphone, which I mentioned briefly trying in this post about Skype. I'm going to download it and try it out, but I initially don't think it has the clout to take out the Skype juggernaut. Am I going to get more than a handful of people to try this out when Skype works today? I agree with Doc Searls, it is a locked silo, which I'm not happy about...but it's here today, it works, and it far surpasses the "just works" test.
What does Gizmo need to do to win my loyalty? Use Jabber for your instant messaging, and run gateways that let me connect to all the other systems with your one client. Solve my too many IM clients problem! (which is actually an identity / buddylist problem in part)
(Actually, yes, I would like to see SIP support in Adium! Where do I send my money?)
Later: OK, gets stuck at "Starting agent..." then "Failed to register with server, an unknown error occurred.", although I did get username "borismann". And yes, there are some "neat" features, like recording of calls, integration of maps and users, and even picking your own "on hold music". Somebody call me when it works.