Strake,
I think that the ditching drills are very useful as a guideline. In many of the ditching cases I studied during my safety courses, the airplane somehow broke into 2 or more pieces or was flooded, but the people who managed to survive did so because they had followed those guidelines. Like in the Minerva Airlines accident in Genoa,1999, where the aircraft was submerged after overrunning the runway. The C/A was instantly killed, and one pax managed to swim to the door and open it thus saving the lives of most of the pax. Do you think he could have done it if he hadn't had a look at the safety briefing/safety card?
Of course an accident happens seldom the way you studied it on the manual! But by becoming familiar with the ideal steps you should be more prepared if/when it happens. That's why I am an avid reader of accident reports. My company issues a safety bulletin with the reports of all our accidents/incidents and all the other's more instructive ones, which I find very useful.