Note that there are two projects with almost the same name: cocos2d-android and cocos2d-android*1*. The latter is a fork of the former and its author did it because cocos2d-android project was almost dead.
In the beginning I was in doubt about cocos2d-android1 (which seems to be a very good work) and cocos2d-x but the possibility to develop in C++ (that I like a lot) and be multi-platform made me chose cocos2d-x.
I'm still trying to learn cocos2d-x.
What I like about it:
List item
it's a C++ framework
you can develop for Android, iPhone, Bada, Blackblerry Playbook, Windows and Linux.
Please, notice that at the moment cocos2d-x team advises that Windows and Linux port are meant for easy your development not for production.
it has a Lua binding
it has a version for Marmalade (a paid multi-platform SDK)
cocos2d-x works with NDK since release 4. Currently I'm using NDK r7. You can develop for devices running since android 2.1 (API 7)
It seems that there are some issues with cocos2d-x on android 4 (what shouldn't be a problem because both it's still not that wide spread and cocos2d-x team will fix any problem they come across).
You will be able to access platform specific functionality like in-app purchase but it comes with a price: you will do almost everything using JNI.
Definitely it's harder than just putting a jar SDK into libs folder and directly call Java functions but it's feasible.
You can develop on Windows, Linux or Mac. For each OS you're using in the development machine the procedures to prepare your environment (cocos2d-x + target SDKs) varies. It's not a problem because you usually will stick with one of them.
Now let me tell you that it's not that easy to debug JNI / Java code. Why? Because there are many steps you must take to enable this and debugging process is slow.
So that cocos2d-x team advices to develop all your game for Linux or Windows and after that everything is up and running you compile it to Android. This way you will have minor problems to solve (if any)
I prefer to develop for android from the beginning.
All in all, I'm really happy coding with cocos2d-x. Community is very passionate about cocos2d-x and they are very supportive.
In the process of learning I wrote two tutorials:
Regards.