Reactor is not bound to Spring, it's an optional module. We want Reactor to be portable, a foundation as Jon outlined.
I won't be confident about pushing in production as we are not even Milestone (1.0.0.SNAPSHOT), in that regard, I would have a deeper look at Akka which is a fantastic asynchronous framework IMO. Also consider Vert.x and Finagle which might be adapted if you look either for a platform (the former) or for composable futures (the latter). If you look after a wide range of asynchronous patterns, maybe GPars will provide you a more complete solution.
In the end, we might certainly have overlaps, in fact we're leaning toward a mixed approach (flexible composable eventing, distributed, and not bound to any dispatching strategy) where you can easily find bits from RxJava, Vert.x, Akka etc. We are not even opinionated by the language choice, even if we are strongly committed to Groovy, people have already started Clojure and Kotlin ports. Add to this mix the fact that some requirements are driven by Spring XD and Grails.
Many thanks for your witnessed interest, hopefully you'll have more comparison points in a couple of months :)
