I did the long (210km) Cyclo version last year. It's one of those "every serious cyclist should do this once" rides - a great experience, even if they don't have a clue how to surface their roads properly.
As the others have said, don't wear anything that can move and rub, don't have anything on your bike that you don't need, and make sure that the bits you do have fitted are securely screwed, taped and cable tied in place. Preferably all three.
I only saw a couple of broken frames and one set of broken handlebars.