I personally don’t have allot of experience with buckfast bees. I am using them in the nucs I am selling because of good things that  I  have heard from other beekeepers. They were originally developed in England as a tracheal mite resistant bee, but they have alot of unique characteristics. http://en.wikipedia.org/wiki/Buckfast_bee

The Koehnen and son queens are both good breeds. The Italians are known first and far most for their gentleness. They’re down side is they eat alot of honey over winter and being that they are an heirloom breed they tend to be less resistant to disease and mites. The Carnolians were originally bred as a large bee for northern most climates in Northern Europe and North America. I don’t have alot of experience with these either, but many beekeepers say that it is a good choice for the first year beekeeper in the rocky mountains because they tend to winter easier than other breeds.