I too had one on my two previous S2k's
I've had one on my NSX for about 3 years and 70,000 miles, and am very happy. Needs cleaning and re oil periodically (I do mine about once a year) and it saves a few squid
I'm sure if you are looking for optimal performance there may be an argument that it's not as efficient as the standard box, as its drawing warmer air from within the engine bay as opposed to the scoop. I think this is probably so marginal that I can live with it.
Current toys= MV Agusta Brutale, BMW K1200s, Mini cooper SD, Jaguar XF, Ex S2000 owner
91 NSX Owner between 16 July 05 and 18 Feb 2011