Re: Powerbook screen markings
The keyboard marks on the 15" come from the keys rubbing the screen slightly when it's closed. The effect is that the satin finish on the screen gets buffed to a shine in vertical dashes. It doesn't disturb normal use (for me), but when the screen is dark, they can be clearly seen from an angle. I haven't heard any complaints about this on the 12" or the 17" PowerBooks, which IMO could be for either (or both) of two reasons:
First, the aluminum case is more robust, making the lid more rigid. This probably cuts down on the center of the lid flexing inward when the PB is closed, making the basic keyboard-screen contact less likely.
Second, the 12" and 17" PowerBooks have that monster hinge that the 15" doesn't. While my 15" (which does, in fact suffer from some key rub) doesn't seem to have a weak hinge, if may be that the more robust hinge on the 12" and 17" models makes any keyboard-screen contact that does occur less abrasive.
Also, I would think that the smaller form factor of the 12" would further reduce any key rub, simply because any play in the hinge would act over a smaller arc.
Anyone out there with empirical evidence on the 12"?