I've replaced about 200 spokes on relatively new bikes in the last few years. Word from several reps and industry types is that there was a gigantic batch of cheap stainless steel spokes that have been used in wheels all across the industry. So far we have been able to cover the work under warranty and have even recieved numerous wheel from the manufactures when several spokes have broken. No one really knows why exactly they suck so bad. The other day an industry guy came in and told us it may have been due to the spokes being double heat treated. Who knows.
Anyhow, the spokes with the N on them are usually the ones that I replace. They are not anything special. If you continue to break spokes I would get the shop you bought the bike from to replace the wheel or give you a deal on a hand build wheel.