I read the entire Airlock thread with great interest since I have experienced a catastrophic (by catastrophic I mean irreparable damage to camera or lens) flood myself. Mine, however, was caused by a user error that would not have been prevented by a vacuum system.
And that leads me to this thread. I'm curious if the vacuum system reveals leaks significant enough to damage cameras, that would not be otherwise be detected by the old and faithful bubble check in a fresh water tank. I do realize that dunking in a tank does not put any appreciable pressure on the o-rings, but it will show you if you have a serous leak.
I'm curious about how many photogs at this site have experienced a catastrophic flood (and I specify catastrophic because leaks that don't cause damage to me are of no real concern beyond alerting the diver of a problem) AFTER doing a careful check of the housing in a rinse tank prior to the dive?
I'm trying to get an idea of the actual, rather than theoretical reduction of risk you achieve by adding the pressure system vs a careful examination of the housing in a rinse tank. After all, it costs $500 and it's yet more stuff to keep up with. $500 is cheap if it saves your camera, of course.