> So yes, you do need to understand the new functional reactive approach. You need to know how to write a Gradle build. You have to understand the complexities of proguard rules. It's all pretty frustrating. But I also feel that many of the skills are more easily transferrable - I can also write a Gradle build for a library or I can use IntelliJ to better debug a servlet. With Swift and iOS, there's only vendor you can build for.

I couldn't agree more. Android experience is hard-won. You have to 'discover' and develop an intuition for application architecture and how to use UI components effectively over time.

The upside is a well-architected Android application --using tools like MVP, dependency-injection, and functional-reactive programming-- will have the positive characteristics of a Service Oriented Architecture: encapsulation, statelessness, composability, loose-coupling. This may seem like overkill for an app, but it minimizes the effect of UI lifecycle issues novice and intermediate developers tend to complain about.

Architect a few Android applications in this way and you gain valuable experience composing abstract services together. A competency that is transferrable to backend services and other platforms.