Great question - here's a few problems that Matt and I have encountered with Github issues and screenshots:

1) Clients, managers and other "non-developers" usually don't have Github accounts. When we tried making them use Github Issues, most of the time they'd use it for a week and then go back to emailing us or just stop giving feedback.

2) When new code is pushed to Github, how do you show non-developers? Usually this requires maintaining staging servers. What if you want to show different things to three different people? Three servers to maintain. With Awesomebox, you don't have to worry about this - we could even send them notifications to check out new versions, so that you don't have to bug them.

3) It's hard to keep screenshots and their associated conversations organized - it requires a lot of discipline, and when building things I've found that I tend to lose track of UI/UX feedback overtime, even if it's within an issue tracker.

4) Not all feedback is an "issue" or a bug. Github Issues are great, but are designed to track problems, not to help people discuss ideas or provide positive feedback.

I hope that helps answer your question - just a few of the reasons that Matt and I started working on Awesomebox. I'd love to hear more about how you work with people who aren't developers, and if our product doesn't fit your needs, tell us what we could do better. Feel free to reach out - brendan@awesomebox.co