It's a community site to validate your idea with pools of "pre-users". Pre-users get added to an email list and when the creator launches, the list gets notified. Users and creators can also communicate with each other providing feedback on the project as well as product updates.
Interesting idea for early stage products as you get both users as well as valuable feedback.
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I actually thought this would be an interesting space for PH to leverage its community. Have ideas vetted and people subscribe to participate because of interest pre-launch.
Looks cool! I think the site is about validating or loosely checking if the idea resonates by people with an interest in tech ('Our mission is to create a laboratory for validating ideas') and not specifically aimed at getting users when they launch. So a step before betalist -- producthunt.
Good luck.
dewey.
Duuce