Neat, but $5? As an /introductory/ price? I don't have a Mac, but I can't imagine it's that troublesome to capture, annotate and share screenshots on one. I guess I'm just not the target market for this sort of thing.
The 'introductory' price is too high, as I think this is a $0.99 type of app, imho. But experience has proven there is a market for everything.