I don't see any reason not to use PureScript, if you don't simply want to do architecture in JavaScript, in a functional style.
Underscore, for JavaScript, is minimal and lightweight and you don't have to rely on compilers that remain experimental. It's experimental enough, writing JavaScript. But, you can leverage PureScript's Haskell-like-to JavaScript compilation workflow, much as one might for ClojureScript, and then, remaining in the Haskell ecosystem under Haskell-style BSD rather than BDFL community licensing, proceed to develop your own IP such that you can write maintainable JavaScript or Haskell code, with Purescript.