Here are some of the examples of Reactive Programming libraries I've found in Purescript and what I've thought about them so far:
Purescript Behaviors: https://github.com/paf31/purescript-behaviors
I've never used a library with truly continuous Behaviors, so this was really neat to try out for me. Really nice to use and comes with utilities for working with browser events already, and gives you good Event modules for picking your sampling options as necessary.
I will probably use this library for all of my future uses.
Purescript Signal: https://github.com/bodil/purescript-signal
Elm-style Signals. If you liked using Signals pre 0.17 Elm and just need something nice to work with, this might interest you. I believe it will probably be used in Pux for the forseeable future, so you may already be bought-in.
Purescript RxJS: https://github.com/jasonzoladz/purescript-rxjs
I haven't used this personally, but it is an RxJS binding, with all the normal Reactive Programming goodness you'd expect. Maybe a little awkward that Observables' create methods always come with effects, but can be quite useful for things like auto-cancelling fetching and whatnot.
Purescript Rx: https://github.com/anttih/purescript-rx
I used this before, but I believe it's mostly targeting RxJS 4 support.
Purescript xstream: https://github.com/justinwoo/purescript-xstream
My small binding to Andre's xstream that I use with my Cycle.js binding. Works fine overall.
Purescript Observable: https://github.com/bodil/purescript-observable
An implementation of ES7 Observables in Purescript. I've also used this a bit, and it was good.
In my opinion, yes. Halogen, for example, uses them for event coordination. In all this cases we build event's source/transformer/consumer graph. The question is which api is more convenient(expressive). And it is open question for me, could we do all things using coroutines, that we can with purescript-rxjs for ex.