[jyl]

What year Prius do you have? They changed the traction control (TC) in appx 2005-2006. 2004-2005 models were more aggressive in shutting off power if they detected slip. By 2007 (my year), the TC traction seems fine. I've gone on a big sheet of glare ice and floored the throttle from a dead stop, the car accelerates smoothly - this is with snow tires though, with the stock tires it would probably cut power. The new 2010 Prius has dialed back the traction control even more. The TC kicks in to protect the drivetrain from overspeeding, as well as to maintain vehicle stability. I surmise they built in some other drivetrain protection and thus could be less protective on the TC settings.

The upill road sounds like one I would avoid too. Sometimes you'll see see a 4WD truck slowly and inexorably slide off the crown of a icy road onto the shoulder, and you realize that some conditions simply aren't meant to be driven in.