I just finished a netmeeting session with a customer using SharedView Beta 2 and it worked really good. It was a bit slow when I took control but other than that it worked good to share applications and chat. I liked how my mouse location showed where I clicked even if I did not have the control. If you want you can also connect with up to 15 people at the same time.
Inside Windows Live Messenger, there is a SharedView menu item on the Activities menu.
Another alternative is Windows Meeting Space. The difference is described to be mainly that "SharedView is a service that allows communication across firewalls with no IT involvement, and runs on Vista, XP SP2, and Windows 2003 Server. It is designed for ad hoc meetings, either face to face or remote (users are in different physical locations). SharedView also provides integration into Office applications and Windows Live Messenger."