What makes it worth your time to beta test?

We just launched our full-stack app hosting SaaS into public beta and we'd like to gather more feedback, but I know it takes time and effort to try out new products.

I've seen plenty of founders just asking for feedback, a few offering gift cards, some giving away free services...

So what would make it worth your time to beta test someone's new product? (Let's assume you have at least a little interest in the product.)