I always tell my destination brides to carry it on the plane and have it hung up front. I think that Fed Ex is great overall, but that dress can't get lost and arrive a few days late - it is truly irreplaceable and one of a kind once the alterations are done!!
I would send it home with a relative you trust, and later get it from them.
I know I am not checking mine in. In one of my wedding magazines they had a story of a bride that did, and her bag was ran over by one of the luggage trollies.
My dress sat in the window seat next to me on the way down to the wedding. On the way home in went in the overhead compartment. We flew jetblue and the extra seat was cheaper then fedexing it with insurance.
Mine got it's own window seat. We used Airtran so no closet on board, and for $69 totally worth the reasurance of not having it out of site the whole time. For the trip home, it went into a suitcase, with hubby's suit and some other items we didn't need. Then his aunt took it home as one of her checked pieces of luggage. I figured at that point it didn't matter if it got a little lost.