On android we always have to deal with the UI elements that we back ported to get the consistent look and feel that users expect.
Guess what you need to do if you use reactive? For RxJava all those UI libs I have now soft forked now have to reference the RxJava View UI elements for me to use rxJava with them.
But, its easier as I already cleaned up the library code so its just replacing certain imports with RxJava RxBinding imports and some minor changes.
And its a nice filter to weed out all the clue-less co-founders and CTOs I do not want to work for.
BTW, if you are adapting Google's DataBinding..guess what? Yup, that work Jake Wharton did with RxBinding..you will have to do something similar to add the Observable to the views and widgets. At least if you want two-way communication between the View Model and the view.
And Facebook's reactive is worse in that it limits you not back porting UI features in the first place and lossing all data when the device orientation changes oh that is game winner right there!