Islamic Law is a set of rules on how to live life and punishments for some crimes. The Quaran and Islamic law however have very little to do with each other. Sharia law is a bunch of rules that a group of judges made up several decades after the death of mohammed. Since Mohammed didn't tell them how to punish crimes and such, they looked at how things were done in the tribal arabian desert where mohammed lived. So sharia law doesn't necessarily prescribe a punishment under islam, it perscribes a punishment under a 8th century nomadic code of conduct. When Sharia law is critisized for being primitive, its because despite the changes throughout the centuries it is still based on primitive, tribalistic, pagan laws. This is why many countries with a muslim majority use secular criminal codes.

People tend to get Arabic culture and Muslim religion mixed up. Most of the crazy stuff exported from the mideast is the result of the old Arabic culture (which, might I add, is crazy), and has little or nothing to do with Islamic faith.