When I visit the root domain I shouldn't be greeted with a marketing splash page, you need interesting content in the user's face right away, entice their curiosity and drive the user to explore the site... even as a fellow developer, my first instinct is to abandon the page as soon as I'm greeted with the cliche startup marketing page. Consider the user experience when I visit reddit.com or news.ycombinator.com or any other link aggregation competitor. What you have now is a tech demo, not a platform. Sorry if that's a little harsh, but I mean well! Good luck!
Edit: You can browse without registering after all, here’s the link: https://non.io/#all (didn’t see it on the landing page or OP post).
My big issues with iframes is the checkout process which inevitably has to make callbacks to your api with the results of the transaction. If you're behind any sort of firewall (like most businesses are) you're in for a world of http pain.
This is also why styling such forms is always some species of wonky.
Those iFrames cause all kinds of headaches when the user hits the back button or double clicks a submit button or does any number of other things that happen thousands of times a day on a moderately high traffic site, and when it messes up you either miss out on a sale (ouch) or charge the customer twice (double ouch).
They usually don't tell you they do. For example, both Stripe and Square use iFrames; otherwise it's not possible to hide credit card entry from your main application.
There are gateways that redirect you away and return you back after payment, but that's a whole another story.