I've heard that the low-fat varieties tend to be lower quality milk, and therefore less healthy. On top of that, I can't stand the taste of skim. I usually refuse to drink it unless it's at least 2%, and I really prefer whole (3%).
Brand name means a lot to me also, because I really can taste the difference between brands. I'm loyal to a certain brand of organic milk because I like the way it tastes.
Another criterion - one that wasn't available in the poll - is packaging. I only buy opaque containers of milk, because I've heard that exposure to light makes it go bad more quickly. Another reason I buy my particular brand of organic milk is that they use opaque paper cartons.