Wow, looks very full featured for a side project. Must have taken a lot of effort to get it to this stage.
I'm an Axure user (also use pixate and framer), so I gave your tool a quick whirl (using Chrome).
I think some of the workflow bits could be improved, for example, here is what I did:
1) Placed a tab container on the screen (iPhone template)
2) Went into edit mode and placed a header on tab 1
3) Copied header from tab 1 and went to tab 2 and pasted it there.
What I expected was that it would place it in the same location as it was on tab 1, but instead it placed it somewhere randomly, so I had to move it to the same location, which takes extra time. I know, it might seem picky, but these little things do matter to me, as it speeds up my work.
Haven't tried the 'scratch' like code editor yet. Will give it a go.
What would you say makes your app better than Axure for example?
Anyway, congrats on launching and wish you all the success with it!