It works sometimes. It is similar to meet with another unknown person in a restaurant or shopping center. The only difference is that sometimes you have an idea about the other's person looks and personality.
Still, you will "know" the another only after meeting in person.
I answered one ad two years ago. It was a blind date. We met in a bar. To me she was beautiful. She is a physiotherapist. It didn't last long but it was fun. With this online dating I saw not much difference than "clicking" with an unknown woman somewhere else.