I guess it depends on certain things, such as the person taking it, how good or poorly it was cut, the type of cocaine(read crack) if they are speedballing it, if they are buying it from shady sources.
For me though, I tried it when I was 17 or 18, when a girlfriend I had surprised me and a couple of other friends before a party one Friday night. I was the last of our little group to try it, finally gave in and snorted a big line. Felt great for about 30 minutes, felt like my hair was floating above my head....LOL... Then, BAM! I felt ill, cut my night short and went straight home. Never again.... however, later in life, I found out that I had(still do) low BP(not to be confused with Bo Pellllini) and the 'caine raised my BP way to high. So I say it sucks, it sucks I say.
Perhaps that is too much, too personal, but there it is. Just say NO! to blow....