A few posts over on the toyota-prius
yahoogroup about it. one or two made
their way into the FAQ section about
You should do far better than most
cars going up that pass. (Depends on
how many people and luggage you have in
the car and the speed you're going.) Don't
expect cruise control to hold out for the
entire length of the pass, though.
I have driven over the grapevine numerous times. The Prius has no problems whatever holding any speed on the grades. However, some prudence should be used if passing. Acceleration on steep grades at highway speeds is a little slow, so you should make sure you have plenty of room to pass and get into the center lanes. (This is probably good advice with most any car, unless you have a muscle car.)
The Prius can overtake a lot of car models that cannot hold the legal speed limit up the grades, and you don't have to worry about the batteries. The ICE will be maxed out in RPMs, but it is generating both direct power to the wheels and electricity to drive the electric motor. There is plenty of battery capacity to make it to the summit, with power to spare.
I am curious if anyone has driven up Pike's Peak in Colorado. Now, that would make a good commercial. A lot of regular cars won't make it all the way.