I had one that I gave liftcontrol when he bought my car becuase I didn't have a stock airpump when I got my car. I used it around the house and for rafts and things of the sort mostly. Compared to the stock pump in my M3, the airman was very weak. It is convienent becuase it has a battery as well as a car plug, but for the NSX spare it would take all day to pump up with the airman plus it gets hot fast.
Moral of the story: it's awesome for beach toys and air beds, but I'd pass for your NSX spare if you have not purchased yet.
Aaron