Well I have not even developed a single game in Cocos2d-x Yet, but just started with Cocos2d-Js and wrote a book last month.
And now when I seriously thought of starting my Mobile Game Development with Cocos2d, they gave the world a good news, and thats the Fastest game engine for Multiplatform development, COcos2d-3.0.
Cool isn’t it??
As per the source, here are the features that xcels par the existing Cocos2d version.
With C++ users in mind
In cocos2d-x v3.0 Objective-C patterns have been completely replaced with C++ patterns.
Class names no longer have the CC prefix (since they are already part of the cocos2d namespace).
Added template containers (cocos2d::Vector<>, cocos2d::Map<>), and deprecated the “base” CCObject. cocos2d-x no longer uses a base object.
A command line tool, which among one of its features, allows you to create new games.
$ cocos new -l cpp MyGame
New renderer is so fast, that we no longer encourage the use of SpriteBatchNode.
Sprites have auto-culling too.
Custom OpenGL commands are still supported!
Fast, really fast
Depending on the game, v3.0 can be 10 times faster than v2.2, or more :).
v3.0 is really fast. Not only it has been improved the rendering performance (GPU) with the new renderer, but also improved the CPU code.
Unified Label API. Instead of having 3 different Label APIs, v3.0 has only one: Label.
Also added glow, shadow and outline support in labels. And labels don’t loose resolution when you scale them up.
Integrated Physics, CCPhysicsSprite. And in v3.0 we went further and added new physics concepts like PhysicsWorld, PhysicsJoint, PhysicsContact, PhysicsShape and PhysicsBody.
A new collection of UI Widgets like: ui::Button, ui::Layout, ui::PageView, ui::ScrollView, ui::Slider, and more!
With Backwards compatibility in mind
v3.0 has many changes, specially internal changes, but still backwards compatible. So most of the old API it is still present, but tagged deprecated.
Also they have just released Cocos Code IDE, IDE for JS and Lua users