I agree, the colonoscopy is well worth it for all the reasons stated above. If a person is having frustrating symptoms in the colon, the colonoscopy gives peace of mind if the doctor finds nothing and decides that IBS is the correct diagnosis. That peace of mind actually helps, because it takes away needless stress from worrying that the symptoms might be something worse than IBS. While IBS is definitely no joke, as I have lived with it most of my life, it is a relief knowing that the symptoms are not caused by something so much worse. I feel for anyone else living with IBS, because it's definitely a miserable condition. I really feel for little kids, because I had problems when I was just a little kid, so I know how miserable this condition is for the little ones from personal experience.
Colonoscopy can rule out functional reasons for pain -- IBS is the fallback diagnosis when the tests don't find anything structurally wrong. So, yes, a colonscopy is worth having, if nothing else so you know nothing else is wrong.
We had a colonoscopy and EGD done on my son -- colonoscopy was clear, turns out his esophagus was swollen, and we had no clue.