I have ordered a new 12" PB combo and first, abstract is right - the "buy a bundle" *does* apply to the 12" powerbook, just not the 12" ibook with cd-rom.
Paperstreet is also correct that apple is relaxing the "take delivery by 9/27" requirement. As the salesman I spoke to on the phone put it, if you order before the 27th, Apple isn't going to hold you responsible for their inability to ship the product fast enough.
If you're a student, buying direct from apple (or from your bookstore if it has good deals) is definitely the way to go.