Butter? Yes!

Nice write up by Whole9; my comments at the end.
http://whole9life.com/2010/11/butter/
[We can’t justify butter] consumption without making some significant efforts to improve the quality of the butter and remove the milk solids.

• Grass-fed or “pastured”. The cows must be grass-fed, or “pastured”, indicating that they are not raised primarily on unnatural diets.  This is perhaps the biggest contributing factor to the overall health of the cow, and the milk it produces.  These cows live outside, are free to roam, and are treated humanely, unlike their factory “farmed” counterparts.  Healthy, happy cows living in their natural environment produce healthier butter.

• Organic. The cows must not be given hormones or antibiotics, or be exposed to synthetic pesticides and other banned substances. While the “organic” label is sometimes manipulated to increase profits, in this instance, it actually means something with respect to the cow’s health and treatment.  None of that junk in the cow’s environment means none can make their way into your butter.

• Clarified. You then must remove the dairy proteins by clarifying the organic, pastured butter at home.  (Instructions for clarifying your own butter are easy to find on the web.)   The clarification process removes the milk proteins, leaving behind pure, golden butterfat. (Just so you know, ghee and clarified butter are similar but not identical; ghee is heated longer, until the milk solids brown.  That imparts a richer, smokier flavor into the butterfat.)

In summary, the only way we can recommend eating butter is if it comes from a humanely raised, grass-fed, organic source, and you take the time to clarify it.  There are no major down sides to butter produced in such a manner, and we can happily recommend you use your clarified butter or ghee as one of your (varied) added fat sources.
Whole9's recommendations are on the conservative side for me.  I've read Dr. Cordain's concerns about dairy, and while there's obviously some risk, the big risk is in overconsuming carbohydrate.  In my view, that's 80% of the problem, and you needn't worry about the other 20% until you nail the first 80% and get your carbohydrate consumption within a safe range, for a long enough period of time that you allow your metabolic systems to heal.  That said, if you follow the above process you get an even better fuel source than can be had by just choosing pastured dairy.

A slice of pastured dairy butter is now like a dessert for me.  It sure adds a lot of flavor and pleasure to eating deli meat!  My kids like it too, even just plain.  Whether or not it has the CLA (conjugated linoleic acid; google it) it is supposed to have, or not, it is at worst a very fine fuel for the well tuned human engines.