Hi Micheal;
Thanks for asking me about my experience. In fact I used to work with in a 3d work flow for so many years. but I started to work in 2d games in the last ~4 years. In this short period of time I had experienced lots of tools, engines and techniques. So, I can tell you what exactly I’m missing with paper2d:
- an atlas tool (as you mentioned it) and it will be more efficient if the user can select several images and build an atlas (convert sprites to one atlas) for a better organizing (atlas builder)
- to be able to see the sprites in the sprite editor, also in the animation editor.
- in animation editor, I really loved it. but selecting an atlas and a sprite per frame is tedious and time consuming. So it is better if i can say this animation clip using 10 frames, then I can fill this 10 frames by dragging and droping from the asset browser into the horizontal down area in the flipbook editor [the area which contain the small boxes representing the frames)
- some times the flip book actor is not appearing the viewport ( it might be a mac issue, as it is not a user friendly computer when it comes to developing games, I’m suing the best iMac exist now, and the engine keep lagging, when I switch to bootcamp windows on the same iMac, The engine is fine !!!)
- changing the pivot via code/blueprint is something essential for a 2d game.
- control the animation speed via code/blueprint [the frame rate], I can find only control the playing status.
- Layering system to make 2d development more organized. So, a user can keep each element in a specific depth but putting it in it’s own layer.
- Switching animations always give a one or two frames black in-between. I didn’t check the C++ code, but I think it is managed by switching the show/hide between different animated sprites
All that to make it better and better. But it doesn’t mean it is a bad tool. It is amazing tool, and one of the best. And I managed to make an entire working level with it & it proved it’s efficiency. Specially when it comes to make a sprite using an atlas image, and the sprite editor shows me a group of all other sprites which built with the same atlas image 
Thanks for making this nice tool !
And I will try to follow with the board indeed. I’m a big Trello user 
so, it is in my bookmarks now 
The core reason behind making this series is showing ppl how to make 2d game within the engine. the second reason was how to make complex mechanics like the one in the 7th episode of this series [rewinding the gameplay data, the 7th in the series and 11th in general]. But it was my mistake to not upload the intro video yet which explain the goals and why we are going to make level from Braid:) Any way, I used abitbucket repo as I do with all my stuff. and I never planned to put it in public as some assets (40%) is not from the open source collection in David’s blog. But I asked Jonathan blow if I can put the project in public and sent him the youtube link, and he accepted (you can see it, it is in Twitter). so, I think I’m still in the safe side helping ppl, and the materials accepted by the owner] and I mentioned that in the repo home page.
have an Epic day
m;