I like GoToWebinar and use it routinely in my work. It is an excellent system, BUT it does have one huge, nasty fly in the ointment – the WMV recording it produces is not properly encoded and you can not directly use normal editors such as Camtasia.
The solution I found in the Camtasia FAQ was to play the original GTW WMV and record the screen with Camtasia’s recorder. This works but has significant downsides – ties up the computer, is subject to picking up unwanted artifacts like mail chimes when you forgot to turn off Outlook, etc.
A friend, Dave Miller, faced the same problem and found the post, “The Ultimate GoToMeeting Recording Guide” which recommends free or nearly free utilities to rework the GTW WMV. A better way to go.