I don't think anyone's actually done it, because most of our users really like Hamlet. That said, switching should be a piece of cake. All you need to do is get the textual result from the templating language you're using and apply preEscapedText to it. Since we use blaze-html under the surface, any templating languages using that library's types will automatically work with Yesod.

Of course, support for type-safe URLs will vary by templating languages, so you may have to manually render URLs yourself, but that's doable via getUrlRender.