I've been spending the last 90 minutes playing with Snagit. School was out 2 hours ago. Fair to say, I love it. Not that there aren't kinks (it's working better with Safari than with Firefox at the moment). But, wow, what it can do!
Notice the really long picture of the blog--it can do a rolling screen capture. Your picture image is no longer limited by the size of your screen. You can even save it as a JPEG2 file, which would allow it to be scrollable, rather than a long file like this.
And you can curve lines, have a lot more control over editing properties (shadow, line size, etc) than with Skitch.
Come the time, I'm definitely buying this!