A First Look at Reactive Cocoa 3.0

Bond looks interesting but also fairly young (initial commit ~ 3 month ago unless I'm missing something). ReactiveCocoa already has several years behind it. It's very stable for Objective-C (several parts of Genius Scan are written with ReactiveCocoa) and now coming to Swift.

These frameworks actually don't require you to rewrite your whole app in a different way: you can easily migrate a few classes or just rewrite a few new classes. I would recommend this as a way to get familiar with functional reactive programming in an applied way.