The NS-10's were originally sold as home stereo speakers, and somehow got popular among studio engineers. Bruce is quite right when he says "if you know the NS-10s shortcomings very well, you can produce good mixes on them, much like any other speaker an engineer might be very familiar with."
I used to use my NS-10's as my main monitors, but now that I have my Wharfedales, the NS-10's are a second reference.