I wouldn't think it would be, but you can get the same effect by feathering the gas pedal. If you want to coast without drag, let off of the accelerator and gently press back down just a smidgeon and you will notice that all the arrows stop moving toward battery or engine and essentially you are in neutral. I do it all the time to get the most distance while coasting. If you see that you will need to stop ahead after a while, I just let it coast regular to charge the battery.
See http://priuschat.com/forums/-vt10937.html which also began discussing the same thing yesterday. Bottom line: harmless, and more reliable than getting stiff-ankled from trying to feather it all the time. . _H*
I can't feather to neutral above about 30MPH. I physically (sort of, the whole think is software/electrically controlled) go to neutral all the time.
