If you're talking about an app-store launch, then it's important to have the core mechanics of the product (from a user interaction perspective) figured out such that the majority of your users are doing the things you want them to do in order to drive continual engagement with the app.

Design polish can come later and often slows down whomever is implementing the development of the app.

I don't think anything should ever be "ugly" but lacking polish is often the right way to go to get speed to market. That said, to be sure of the core interactions, you want to do as much testing and observing real users use your app prior to launch.

Happy to talk through any of this in a call with you.