Flat UINavigationBar with "glyphs" instead of "buttons"

Everybody is moving the design of sites and applications in the flat direction,
I found myself struggling a bit to achieve the new common NavigationBar look.
To hide the common UIBarBatton background just add this call in your app delegate ad it will be gone

[[UIBarButtonItem appearance] setBackgroundImage:[[UIImage alloc] init] forState:UIControlStateNormal barMetrics:UIBarMetricsDefault];