Heroin is pretty nice, it makes you feel really warm and fuzzy. I am no addict but I would say it's high up there on my list of favorites. First time I did it was a bag shortly before going to work, except when I got there I felt like I was in Heaven instead. I did puke a little bit but with heroin it's not all that bad, mostly liquid and you can barely feel it.
It does take a good deal of consecutive use before you get physically addicted, people should be sensible enough to realize they can't do it that much. Also makes you very tired when the effects are wearing off.