Hi,
I was playing with this tool a little, not much to be honest but enough to have few thoughts.
Initial thoughts:
Cool to have something like that but I have no idea how to use it and interface is not easy enough for me to get without manual.
I had some UI bugs where there was no BG on buttons and I was getting confused what’s what.
I feel that there are not too many options and the one are in are not as well laid out as they could be.
After short time I stopped working with it as I couldn’t get my head around it properly.
What’s next?
Corona definitely needs editor like that and you have my full support on it. I look forward to see new version and improvements as almost all the other engines got editors and I know it’s a massive help with games and apps.
As for inspiration I would go towards Construct 2 which is an awesome tool and whole engine is based on visual editor. Their tool is very mature and editor is just great so if you can please inspire from them in this matter.
Thanks for the chance to look at the composer and hope to see more very soon 
M