While I was shooting today (I was using a shotgun receiver) I managed to squeeze off one shot instead of a semi-shotgun quick pull. To my surprise, nothing happened except a click of the hammer when it hit. I had to scratch my head for a minute before I realized the hammer released, but the transfer bar wasn't pulled up to allow the hammer to hit the firing pin. I just recocked and gave a little healthier pull and everything went as planned!
I actually feel a little better knowing the transfer bar system on the NEF will actually prevent accidental discharges!