I have been through the security checkpoint many times, and I have had different experiences depending on the airport, and the country. I've never experienced a security checkpoint where I saw them actually catch someone or something risky, but I think they do a good job at making sure everyone goes through the metal detector, and they pat people down to make sure they don't have anything on them. However, I have gone through checkpoints where no one cared that my water bottle was completely full, or certain checkpoints where I was able to leave my coat on, etc. It just depends on the airport.
