Rated 4 out of 5 stars
This plugin is a real time saver, most of all if you're doing things like giving feedback during web development or writing a book which requires annotated screenshots.
I think it would deserve 5 stars with a missing "killer" feature, inspired from the Linux app "Shutter". In shutter you could add "autoincremental" markers to a page: simply put, you could click n times on the image and have circled numbered markers (1, 2, 3 enclosed in circles) put on the page automagically. This is a great boon if you're putting references on a screenshot for external reference (in a text or feedback mail, for example).
With this plus ìt would become THE definitive screenshot tool to me.