Redbooth is fantastic for freelance artists, small businesses, or even larger companies. It's versatile and can handle and help you stay organized. IT has replaced most every other tool we use to stay up to date on projects, keep track of tasks, and use it for a proofing space. It may not be good if you aren't a freelancer or someone who has many tasks to complete. It seems best when there's at least 2 people in the company.
If you have more than 2 developers this thing is basically a requirement within github to manage sprints if you use agile methodology. Why use a different website entirely when you can run your entire board right from github itself? I've tried other solutions but basing everything on github issues makes it so no duplicate work has to take place. If the UX quirks and mobile were fixed this would be 10/10 for me! If you're only one or two devs on a team it may be overkill to use, but if you're going to scale it's better to put the process in early.
ZenHub is one of the best GitHub repo-management software integrating the usage of work-boards and task management, with the ability to integrate several team members to the work table. This method makes the team more organized since everyone can keep track of their time and tasks of themselves and also others, so you can see how fast your teammates are working or if they need any help with something they're working on.
Support is good, but quite honestly, I haven't needed any support since 2015. As I remember, I was required to open a ticket and had to wait a few days for resolution. I give it a rating of 8 because of the lag in getting a solid resolution, but it was resolved adequately.
I have used Workfront in the past, which in my experience, is best with a traditional waterfall methodology, similar to Microsoft Project and the other more traditional project management software projects. ZenHub is truly designed around the agile methodology. Other products that claim they are agile oriented seem to just be adjusting and tweaking their traditional product to include a few agile features.