Much to my disappointment, I found out last week that my up-to-date coupon for Panther (from my new PowerBook) is not redeemable in the Apple stores — they have to mail the OS upgrade to you. Luckily, I can fill out all of the required crap online instead of having to fax/snail-mail it to them.
I've been looking forward to Panther for a while. I'm kind of bummed that I can't just download a disk image and burn it. No matter, it should be here sometime next week.
In the meantime, have a look at Mark Pilgrim's What's New in Mac OS X 10.3 Panther.