On heroin: Opiates are far less harmful than smoking, as long as you don't overdose (which is often caused by improper labeling or mixing with other drugs). You'd be surprised how many professionals are using opiates (such as time-release oxycodone) daily. Again, the difference is in using it for the mental advantage, not IV'ing it to get a rush and high.
It's just that in general, you're not going to have such people confess their usage due to negative social stigma. Thus the only "addicts" you see, are the ones that couldn't hold a job, couldn't get a supply (it's generally easier to buy heroin than proper opiate pills), and so on.
At least that's the story you'll often hear at family group meetings. Not the usual homeless drug addict story, but people keeping up appearances while hiding some pretty big problems.
My brother was a functional meth user for many year before he lost his fiancée (mostly because of the anger outbreaks and lies, we didn't know he was using then), then his license and car, and finally his job. Of course then again there may be far more people that just continue using without ending up in the same situation.
Don't by into the "addiction is bad" story that DARE and the like sell.