well here's my story, take it for what you will.
after reading everyone's story, i was ready to walk into my local apple store and stare into these god awful lines on the new 15"...the 15" i just ordered over the weekend. i fought through the crowd and saw 3 different 15" powerbooks. i thought this was too good to be true, i'll look at all 3...and i did.
i must have looked like a real goon staring at the display all squinty eyes from 3 inches away...but after looking at all 3 displays for god only knows how long..the only place i could see the lines was on the blue desktop/background (new to mac, dont know what you guys call that

) i was relieved beyond words. i did see the lines though...but i opened pictures, i opened CS2, i opened espn.com...on all of these. this is something i would be incredibly anal about and i absolutely would notice this type of problem immediately.
i had a friend with me as well, who stared with me...same deal. only on the background did we see these lines. stood it up side by side on the 17" too...did the same thing on that one.
in conclusion, i walked out of the apple store with very little to almost no concern that my powerbook will be fine. maybe i'm not as affected by the lines, but we had 2 sets of eyes, both of which came to the same conclusion. looked good to us.
i hope this puts the people in my same position at ease...at least somewhat. best of luck to those waiting for theirs in the mail, just like me.