The iBook is designed for it, but I wouldn't buy one now.. wait until April.
I have taken my PB all over the place and it has stood up to it well. All you need is a skin and a well made backpack and your away....
I have been reccomended Booq bags on many occassions as people swear by them, but I have a cameraback with a laptop slot that does just nicely.
The ibook can't take a more severe jolt any more than the PB (well maybe slightly), but it can be shoved in and out of a bag without losing its rugged good looks.