There are acutally a couple of other great threads here on shipping wine back.

The wine box will be find, but put a layer or two of newspaper on the bottom and the top, depending on the inserts you get. Some are pretty cheap, and the bottle will pop out the thin styrafoam ring at the bottom. If you are by Sterling, they have (or did) nice ones for $8 for the 12 bottle size.

Saying that, I've pretty much switched to putting them in PVC pipe in a suitcase. Cut to the right length, you take the pipes out stuffed with clothing and on the way back you put the bottles in and use your clothing to pack the ends of them. Then it's just a suitcase, and not a wine shipping box that screams "My owner isn't here, take me home and enjoy a case of wine" at the baggage claim area.

Fragile or this end up will have no bearing on how it's treated, and if they drop it things will break in the carriers depending on which end it lands on.