Here's some more info on the NSX-R that I gathered today.
Playing time: about 12 minutes of continuous play
Charge time when car is fully dead: 13 minutes
Charge time when car can't run but headlights are still on: 13 minutes
Amount of time headlights stay on after car can't run: 5 minutes
I found this interesting, because the headlights stay on for a long time after the car stops running. I thought this would have a major effect on the charge time, but it had no effect at all.
By the way, I'm still using Rayovac Ultra NiMHs in my controller. I don't know if using disposable alkalines would make a difference in charge times, so I'll pick up a pack of Energizers next week and try it out.
I'm having a very positive experience playing with the NSX-R, in case anyone is curious about that. To me it's worth paying the extra money for this car, not just for the front and rear lights (which have major visual impact if you like to show off your car to friends) but also it controls a lot better than my Cox Beetle. The Beetle, while fun to play with, is a lot stiffer in turns and tends to spin out a lot. It seems like some things were improved on the internals of the NSX-R but I can't confirm that, it's just what I think from playing with the car