My company used JS buildings for several iOS projects with great success, but on the Android it is just nightmare. It is absolutely unreliable technology.
The biggest problem is NO ONE WARN about POOR state on technology on Android.
If you download latest stable release of cocos-2dx and will try to run ANY sample on e.g. LG-P500 480x320 that NOTHING will work. It works sometimes on tablets, but it mostly fails on phones. It is very hard and time consuming to debug it.
I have no hope that developers of cocos-2dx will fix, but I want to warn people who do real-life projects NEVER use it and never start Android project with JS bindings.