I don't think I've ever utilized an AppSumo purchase over months as much as I have utilized Fable in my time of recent ownership. I am an IT provider and am using Fable to create walkthroughs for my internal IT team to follow in lieu of screenshots and tons of text. Next I'll be using Fable to create technical walkthroughs to empower my end-users. I don't have any intention to use Fable for sales, but I can see them being wildly successful in that market space given the extremely flexible functionality of the product.
Cons: 1) The workspace automatically resizes and pans around - sometimes when you aren't expecting it. I've accidentally 'thrown' an annotation slide around the workspace because of this. Annoying but easy to work around. 2) There's no way to export your projects externally, meaning that if the company goes belly-up in the future, all of your hard work is lost. We want the best for these SAAS companies, but it's also important that we as customers have a way to protect ourselves and the content we create.