Sentencing criminals???:
I think people sent to prison for drug abuse should be in rehab centers.  Note, that's drug abuse, not selling drugs. Drug dealers should have prison time, but the punishment should fit the circumstances.
If the drug abuser commits crimes to feed his/her addiction, then jail time for the criminal activity, followed by rehab for the drug abuse.

As for murderers and rapists, I think the sentencing needs to be harsher.  And capital punishment needs to be enforced better than it is. 30 years of appeals and going through the legal system for a capital murder is too long for justice to be meted out.