Pixelic

Simple, straightforward, it does what it promises without getting in the way. I just tested it and it was flawless at the first approach. I wrote a short review for it here: http://tools.robingood.com/3128041/get-comments-and-corrections-directly-on-your-visual-drafts-feedback-by-pixelic

Amazing idea and implementation. My suggestion is to have an integration with Jira too. Many companies include Designers (and almost everyone) on Jira. Also, what about an API in the future? So it can be used with Zapier or its alternatives, for example.

Great idea and smart to integrate with Slack. Really liked the work Kanban. The pricing stopped us. $12 per user per month is high. Maybe as the product continues to evolve and further value is added. At this stage is more of a nice-to-have than a must-have.