I have tried Metal Master brake pads. I don't recommend them for anyone. In fact, I don't recommend getting any "generic" brake pads from your local auto parts store. They make LOW performance brake pads that are the proper size and shape to fit in the NSX caliper (because they also fit certain models of Legend and Prelude), but they are inadequate to the performance requirements of the NSX, even if your car never sees a race track.
I have tried a lot of different kinds of brake pads. Any brake pad is a trade-off of a number of factors - braking grip, resistance to heat, dusting, noise, price, need for warmup, etc. I disagree with White94; I think the stock pads are excellent, for street use as well as on the racetrack. However, they are somewhat more expensive than many aftermarket pads.
Right now, my favorite brake pad is the GT Sport, which is made by
Cobalt Friction. It has excellent grip, but is user-friendly for street use (unlike track pads which squeal, dust, and need to be warmed up to be effective). Highly recommended.
As far as brake jobs, the cost depends on which pads you get. If you buy the pads yourself, it generally takes an experienced mechanic around 45 minutes to change pads on either axle, although you'll probably get charged for a full hour of labor. Labor rates vary from one city to another and between dealers and independent mechanics; around here, typical hourly rates are $80-110. There is nothing unusual about the NSX brakes that requires someone with NSX experience; any competent mechanic should be able to do an NSX brake job.
