Actually that's pretty standard language among the waivers I see, and they probably got a form waiver from their parent organization rather than having it drafted specifically for them.
I HAVE refused to sign waivers with language like that when it was from a doctor's office. (And they were cool about it. If they hadn't been, I'd have found another doctor.) When it's boilerplate for participation in an event, I go ahead and sign it for the same reasons Geonz pointed out.
Speed comes from what you put behind you. - Judi Ketteler