RealMilk.com sums up alot of the issues and studies: http://www.realmilk.com/rawmilkoverview.html

NUTRIENT DEGRADATION BY PASTEURIZATION:
Vitamin C , Calcium, Folate, Vitamin B12, Vitamin B6, Vitamin A, Vitamin D, Iron, Iodine, Minerals

Many studies have linked consumption of pasteurized milk with lactose intolerance, allergies, asthma, frequent ear infections, gastro-Intestinal problems, diabetes, auto-Immune disease, attention deficit disorder and constipation. During a period of rapid population growth, the market for fluid pasteurized milk has declined at 1% per year for the past 20 years. Fewer and fewer consumers can tolerate pasteurized (and ultrapasteurized) milk (Don’t Drink Your Milk, Frank Oski, MD, 1983).

The Protective components of Milk are generally destroyed in Pasteurization process:

PROTECTIVE COMPONENTS: Raw milk contains numerous components that assist in:

Killing pathogens in the milk (lactoperoxidase, lactoferrin, leukocytes, macrophages, neutrophils, antibodies, medium chain fatty acids, lysozyme, B12 binding protein, bifidus factor, beneficial bacteria); Preventing pathogen absorption across the intestinal wall (polysaccharides, oligosaccharides, mucins, fibronectin, glycomacropeptides, bifidus factor, beneficial bacteria); Strengthening the Immune System (lymphocytes, immunoglobulins, antibodies, hormones and growth factors) (Scientific American, December 1995; British J of Nutrition, 2000:84(Suppl. 1):S3-S10, S75-S80, S81-S89).

PASTEURIZATION HARMFUL: Many of these anti-microbial and immune-enhancing components are greatly reduced in effectiveness by pasteurization, and completely destroyed by ultra-pasteurization (Scientific American, December 1995; British J of Nutrition, 2000:84(Suppl. 1):S3-S10, S75-S80, S81-S89).

Pasteurization allows cows to be raised under deplorable circumstances. If the cow gets an infection, just pump it full of antibiotics and pasteurize the milk until it's sterile. Under these conditions, cows can be fed grains and raised in confinement, which alters the nutritional profile of the milk. If you're raising cows for raw milk, you actually have to focus on the health of the cow. This begins with focusing on the health of the grass and keeping the cow really healthy (the feds are sadly overzealous in targeting raw dairies), so that means avoiding things like CAFOs, which are basically concentration camps for cows.

Two of the best resources for more info:
The Revolution will not be Microwaved by Sandor Katz
The Complete Patient Blog

In really simple form, pasteurized milk does not have lactase in it which helps you digest lactose. Raw milk does have lactase so the lactose in it is digested more easily, hence why it is less problematic. So you get a power house of vitamins and minerals without potentially the problems associated with dairy.

I got crucified the last time I posted about raw milk. But I'm a Dairy Scientist so I can't just stay quiet. First of all, I am not going to debate raw vs. pasteurized milk because on a Paleo board I am very outnumbered. But, not every farm you go to that pasteurizes milk treats cows badly. Of course, I am speaking for my own company here and have physically been to the farms. I can't speak for others but want to get past the generalization that "Pasturization allows cows to be raised under deplorable circumstances). For my Dairy, Cows who develop mastitis and treated with antibiotics are isolated immediately and never brought back into milking rotation. They are raised as calves on a feedlot, which looks like rows of large dog houses, but they are allowed to roam free. When they are of age and bear their own calves, they are brought to the main pasture, which is just that- a huge open field of grass. There is also a 1-mile long open-air barn- essentially a translucent plastic roof with no walls and no doors, where they are allowed to wander in at night and when it rains. When they are in the barn, their feeding trough is filled with harvested grass. Both lines are also fitted with specialized "mattresses" for the cows. There is also a robotic machine that goes down each line daily to clean the manure while the cows are out to pasture. The milking process itself is done in a Carousel-type milker (all cows enter and are milked in a circle, facing towards the center while the milker slowly rotates). It has been shown that the slow motion of rotation makes it much more comfortable for the cows. In many commercial milking operations, the cows will defecate while milking because they are uncomfortable. The way to tell if a cow is happy is if it is chewing it's cud. When a cow has stopped giving milk (depends on the cow how long this is), she is brought to the "Retirement Barn," where she just lives and feeds until she naturally passes. So, my suggestion to you is before you make your decision, do some research on how the cows are treated, no matter if it's from a commercial Raw Dairy or a local farm. It really does depend on the company.