The visual aesthetics of Stripe's output demonstrates great taste. But it's the way that taste complements the functionality, and how they are uncompromising about functionality and usability. I've worked on too many UI's where a detail in the design has compromised the usability, performance, or functionality of a UI all for the sake of aesthetics. I swear I might kill the next UXer that tries to argue that "responsive is out of scope" just because they can't be arsed to figure it out or change their designs to work responsively.

A lot of products and services look like Stripe now, or at least try to, but very few work as well as Stripe's output.