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Pros
Pro Intuitive, easy to get started with
It has an attractive, intuitive interface; supports several canvas sizes; has several editing tools (pencils, pens, brushes, erasers) onscreen. There is a timeline of panels at the bottom and an animation mode. It seems to have all the basic features one might need to storyboard a project.
Cons
Con There are clues that development may be on hold
It's not definite, but the website copyright hasn't been updated in 2 years. I'll update this if I start receiving up-to-date newsletters from them soon, but I fear their interest in developing this open source product might be waning of late.