0plus1 That's OK, everyone's entitled to their own opinions. Our philosophy is that developers should try out what's already out there(even use the competition) and choose the technology that best solves their needs,but we believe CocoonJS is the best way to deploy,accelerate, and monetize HTML5 games.
As for the other questions, the CocoonJS platform can easily add extensions to sit on top of our platform such as game center. We already have built in extensions(easy as calling the functions)- you can see our wiki for the list: http://wiki.ludei.com/cocoonjs:featurelist
We also have many demos with the source code to see how you can integrate some of them:
http://cocoonjsservice.ludei.com/cocoonjslaunchersvr/demo-list/
Also, you can begin selling your game as soon as our cloud compilation system is done, which will be pretty soon.