Here’s an excellent and useful summary of the appendix from a surgeon’s perspective. Creationists dislike the idea that we bear useless organs, remnants of past function that are non-functional or even hazardous to our health; they make up stories about the importance of these vestiges. Sid Schwab has cut out a lot of appendices, and backs up its non-utility with evidence.
The study I cited most often to my patients when asked about adverse consequences of appendectomy is one done by the Mayo Clinic: they studied records of thousands of patients who’d had appendectomy, and compared them with equal thousands who hadn’t. (Back in the day, it was very common during any abdominal operation to remove the appendix. Like flicking a bug off your shoulder. No extra charge: just did it to prevent further problems: took an extra couple of minutes, is all.) The groups were statistically similar in every way other than presence of the worm. There were no differences in incidence of any disease. It’s as convincing as it gets, given the impossibility of doing a prospective double-blind study.
I have a personal interest in this: I was nearly killed by my appendix at the age of 9, and had it removed. I haven’t missed it since.