Completely agree. Some of the unhappiest engineers & designers I know are on teams trying to copy the company's iOS app on Android.
We were admittedly in the position you describe: a company of majoritively iPhone users who shipped the web & iOS apps, cleaned up the API and were starting on Android.
We also ordered a range of devices and hooked them up to our Play Store alpha channel so every build had to go through the 3" phone and 10" tablet test.
Finally, it helped to have a couple hard core Android users on the team who could explain why simple features like the 'back' button are truly game changers. There's a good post on some of these differences here: http://paulstamatiou.com/android-is-better/
However, in our v1 the only fragments that share an activity are our main feed & story view. All other's have their own activity. It made data flow a lot easier, our manifest file a lot cleaner when filtering for intents, etc.
I'd say the two most important libraries for our app have been Retrofit & Picasso. Both are built on RxAndroid so using it as well is a natural extension. I think most people would probably only need RxAndroid or otto but we've enjoyed using both. We mainly use the former for chaining network calls and the latter to maintain a bus of state updates.
Dagger 1.x (which we currently use) certainly helped slim down code size but it's mix of compile time and run time injection made using tools like Proguard a bit messy. We haven't made the jump yet but it seems like Dagger 2.x solves for this: https://github.com/google/dagger
Butterknife is just plain useful to avoid a ton of view boilerplate code.
Our app is admittedly not too complicated but so far we haven't seen any performance issues.
