Hello. I just want to say that I have what seems to be the same problem. On the right corner of the palm rest of my G3 iBook (baught this autumn) there is a rugged "x"-formed crack just where the case rounds the corner. It doesn't go all the way, but I'm afraid it will develop into a full crack, thus deforming the palm rest or something. Anyway, this is not the way it should be, so I think we'd be entitled to free repair. The question is how to prove that it actually isn't caused by some external cause etc. And, as you point out, it's not a very tempting option to be without the book for weeks or months.
Lars Erik