Sweeping Release of Liability - Any real protection?

Dear Trial Lawyers of the Straight Dope:

Do “permission slips” that state that you are releasing some entity (and all contractors, agents etc etc etc) from “any and all liability” really provide the entity with protection against suits for negligence?

Years ago, as I was preparing to take a group of adolescents from a psychiatric half-way house on a camping trip, I asked the hospital attorney for advice on what specific language I should include in the permission slip to protect the hospital from liability.

His refreshingly candid and common sense answer: “A permission slip is a good idea, but it does not really matter what the wording is. Negligence is negligence and it is Dr. <Blank’s> ass if you screw up.”

I am interested in hearing from Trial Lawyers or Judges with knowledge of actual cases or case law. I am fully aware that “anybody can sue about anything”. When they do sue, does the sweeping permission slip provide any protection?

PS: I agree to hold harmless and I release from any liability any person who provides information in response to this question.

Yes, they have some value. In my state, they generally are upheld. There are limits, though.

I’m not your lawyer. This isn’t reliable legal advice. See a lawyer licensed in your state for that.

It’s also a question of informed consent.