For "YAHH," it depends on the context of what you are looking for. If you want to listen to a real rap song, then yes, it is a terrible song (one of, if not, the worst). With that said, if someone is getting on your nerves and you don't care about listening to real lyrics, then it's not that bad.
Don't get me wrong though, I am in no way condoning or promoting what Soulja Boy does (He's the George Bush of rap). In a way though, you can't really blame him, he's making money off of something he made up. I blame the record company that signed him because they wanted to make his music famous (the guy was "discovered" through Youtube).