Pro Easy integration of 3rd party plugins
For example, if you want to add a rating plugin, you use
sdkbox::PluginReview::init(); and if you want to add the Vundle Ad Network SDK, you use the one packaged in SDKBox
Cocos2d-x is not only open source but also supported by Chukong Technologies of China and USA.
Regularly updated and adding support for the latest technologies. 2014 has already seen the release of Version 3, a new Cocos Studio development toolkit (optional) and support for new technologies like skeleton animation systems Spine and Adobe DragonBone.
Pro Supports 3D models with skeleton animation
A new feature since Cocos2d-x v3.1 is support for 3D models (in your 2D game), not only this but support for skeleton animations is included too! This awesome feature allows for impressive characters in your game along with easier, more fluid and realistic animations.
Con Poor documentation
Most existing documentation is out of date. API documentation sometimes exists, though is usually just a one-liner and more often than not is completely absent. New features and significant system rewrites often make it to a major release without a single line of documentation accompanying them. Cocos2d-x family is developed by Chinese mostly, so market outside of China is not their main priority. Some tools (like Cocos Studio) have China-specific services and markets.
Con Poor support and non-existent community
Up until 2013, this was one of the best engines around. However, since then it was bought by a Chinese company and began stagnating - it's virtually in a slow death. Most developers abandoned Cocos in favor of more modern solutions leaving the community weak and the forums with little or no traffic. Although the Cocos2d-x Forum seems to have a decent community going.