Yes, I've heard of it, and actually was diagnosed with it before that diagnosis eventually went to ADHD. Both are definitely overused, and so many people tack on a diagnosis after very little actual observation. I got my diagnosis at the age of 16 after almost 3 years of various types of therapy and observation. True to the actual "disorder" profile, it has gotten worse with age, not better. I, too, wonder about the actual existence of "oppositional defiant disorder," and wonder if it's usually a symptom of something else -- maybe a disorder, or maybe a symptom of overly lax parenting.
It seems that the vast majority of people who are diagnosed or self-diagnose don't understand that it's the severity of the symptoms that make it so-called abnormal. Most of the adults I hear that say they have it think so because they have trouble focusing on everyday life, which is such a tiny aspect of ADHD, and they don't realize that the vast majority of the population is over-stimulated and THAT'S why they can't pay attention. Most of the juvenile cases I hear seem to be just kids being kids, responding to their environments as you'd expect perfectly normal kids to respond. If someone "gets over it" as they get older, then it's almost certainly misdiagnosed.