I personally feel crows are a big headache and what ever method we try they try to overcome it they are very clever.
i have a dog so i dont have the problem of running after the crows, my dog does that work. even at times it too gets so irritated that it will just keep quite even after seeing the crows.
Just, if you are having a problem with them roosting on your roof try putting some moth balls on the roof. You will have to replace them on occasion but I've seen this work before. Helps with keeping squirrels away also.