Lord knows I plan on inspecting the hell out of the NSX I eventually buy...the last thing you need to deal with is a faulty sports car you just bought, that can be a big financial headache.
Word of advice: try and buy it from someone who babies their car, and takes real good care of it. If they don't know what wax is, or haven't been waxing the car every 3-4 weeks MINIMUM, they don't love it. And you can't trust them that they've taken extra special care of your soon to be NSX.
If you can find one that is being sold by one of the folks here on the boards, or similar type individual, grab on with both hands and drive home with it.
Good NSX's are out there, and you don't have to get THE NEXT ONE YOU SEE, you can be patient - get the one that feels right.
If you've never driven an NSX, and you'd like to get a feel of what a proper NSX should feel like - its easy. Just call up an exotic rental car company, and rent out the NSX for half a day or so. These operations typically rent out nice cars for use by businesses and teenagers looking to score on prom night
Now that you've driven around nice and hard with that rental (you weren't a pussy with it were you?) you should be able to gauge if there are any problems to the NSX you're purchasing...