1)I think you made registration process a lil bit too complicated(wait 2 days just to get link, then unzip password protected archive)
That is protection from fools, you know, any body can just unzip it and distribute.
I prefer just simple download and use system, current one seems to me a lil bit weird.
2)Some times GameStudioHx can crash on build(on first launch)
3)I think you should follow GIMP drag and drop style without need to switch between two modes(select and drag and drop)
4)I got crash on Ctrl-Z
5)Particle systems are running on CPU, I see that you made a very impressive job on particle editor, and I understand it's very hard nowadays to make it run on GPU, but
it would be cool to have it running on GPU, but maybe performance is ok for many games, I'm not sure.
6)I'm not sure if particle editor will fit on small screens
I wonder if that is the same project that we seen project called NME world builder...
http://nmeworldbuilder.com/ seems like it's same GameStudioHx, I wonder why you need both websites for same project.
I will take a look again at your GameStudioHx, but right now, I think such a great project have a good chance to be crowd funded or maybe sponsored.
I am pretty sure that many people just been dreaming to get such game studio for OpenFL, if it could provide a decent help in game development(it looks just amazing) or maybe even more simple work flow for game creation that would be just great!
I just need to try it more to understand how to use it.
It seems like you spend a lot of time to make one.
By the way web site looks very professional and good.
Anyway great project! You did amazing job!