I've just downloaded the trial version of SnagIt for mac and I'm sure I'm missing something obvious but I can't figure out how to drag a captured image to me desktop (if that's possible) like I can do in Skitch.
I'm thinking that you don't have the tray displayed. Go to the View menu and select Show Recent Captures. As a result, a tray of thumbnails of recent screenshots will appear along the bottom of the editor window. With that showing, I think you will see what I mean.