Really Cool. This would be perfect if it had the ability to “select a region” and then add notes to that region. Similar to Google Docs Notes ability. As a Developer, when I hand it off to review, I could snap a screenshot and send it to the designer (along with the site) and when he has any edits, he could mark them on the “page” instead of making a huge Google Doc and I have to try to interpret what part of the page he is talking about.
This tool being online is the key part of why this would be useful. We use a program called “Invision” that lets us do this with Designs when we show clients wireframes and mockups. The screenshot tool would allow me to see the whole page and notes tagged in certain spots of the page for me to look at.