The riding in heavy traffic portrayed in the video is absolutely normal for an urban cyclist and is actually quite safe. I personally don't use a horn but sometimes I think about it. To ride less aggressively in a situation like that seems (to me anyway) to negate a lot of the advantages of bicycling over driving. Also, I don't think motorists are as upset about it as we cyclists sometimes think. One thing is that the camera angle makes it seem a little more "hair-raising" than it actually is.