I liked the Sketch sprint feature that generates a timelapse - you draw for a set time and it makes that into an animation. But it also reminds me that I need to play with the Slate (via iskn) again and I'm hoping to hook it up to StoryBoarder if possible (next experiment)
But I did play with it and generate an animated gif (just using mousepad and finger to draw very roughly) - it's not very sophisticated but it is quite fast and fun. You can likely spot the mistakes but a bit of practice will help (as with most things).
UPDATE: So, it turns out (thanks to someone asking in the Facebook group) that if you scroll down on the right hand side you will get the Shot Generator. It doesn't look as if you can scroll but you can