My app has a UILabel formatted as an NSAttributedString with the attribute: \'NSKernAttributeName @1.9,\'
OK. I had the same problem (see comment above). It depends on the font (I used Courier as well). For some strange reason Courier does not support kerning (in iOS7!). Use CourierNewPSMT and everything works as expected .... at least for me.
BTW: Here is a nice list of fonts on the iphone: http://iosfonts.com/