This is a technical site, some technical details of the implementation would be more appropriate.

In terms of the app itself, web apps generally offer some way to fire them up straight away without having to sign up. Many users, myself included, will just click cancel on the sign up screen. You have to give us something first before we trust you with our email. Edit: I ended up looking by just entering a rubbish email address.

The landing page is very pretty, though the app looks somewhat like https://moqups.com/ at a glance.