> ... my own interface builder ... Nice, but you have a "Try it now" button on the first page, that suggests (at least to me) that I can try it right away. When click-ing however, on get's a "Login with..." page.

Would be much better if users could try it without login, and only if they really like it and want to save their work than would be a login required, or when they start to use it professionally.

I think for demo/show purposes, lowering the "entry" is always better, as it will get more people to really try it.