as a fellow italian user I'll spend some word about this issue.
I'm the only one to have an app (not properly a game, more an education tool) on the appstore made with c2 (link)link, I'm also in the process of finishing another game.
That being said, since the last time something has changed, code has been optimized for mobile and there is (finally) an option for having retina graphics.
That being said we are still a long way to achieve decent performance. My latest game ha been optimized to insane levels, and still I get fps drops that go as low as 5 (from steady 30fps), all this with phonegap.
I find that the issue with mobile here is that Ashley is betting on AppMobi and CoocoonJS that are both canvas accelerator (and work very well in that regard), the problem is that AppMobi is pushing its own services (so no plugins) and CoocoonJS is having clearly problems to get published on the appstore, and still a long way from an online building service. In the end it's a good commercial choice because most of the people here do not have a mac and don't want to fiddle with code, but this will limit c2 games to unprofessional games, as for example there is no support for game center in neither of those solution, while with phonegap (compiled by you with plugins) is currently possible.
As I see it, as of today, if you want to publish a professional game on the appstore (with gamecenter, iAP, iADS and modern monetization solution) the ONLY way is to use PhoneGap in xCode, and you have to get your hand dirty in code to optimize PhoneGap a little. I mantain that PhoneGap is the way to go as the sourcecode is publicly available and there is a lot of room for customization, if someone could add DirectCanvas support to phonegap we could have a real mobile solution.