As I was utterly impressed with my Nokia N9 the first 4 weeks, I am so frustrated with it for the last couple of weeks that it made me return to an iPhone 5.
For no apparent reason my N9 in the midst of a call gave up on me and from that moment on did not want to recognise my SIM card any longer. Despite all the flash attempts I did (which only ended up in a phone becoming more unstable actually) I couldn't revitalise the phone to a state that it became usable again. To me this is unheard of for a brand new phone and it has certainly changed my opinion about the device.
I have now returned it to Nokia Care to have it fixed but I can't see it to become my primary phone device again, unreliable as it has proven to be.