That is a huge amount of butter to put in a home mixer, and the recipe doesn't say that it should be soft, so as a result, I broke my KitchenAid stand mixer that I've had for several decades. I was stuck trying to mix it in a food processor and probably it didn't cream up as fluffy as recipe intended. Definitely should have experimented with half the amount first. Also, I agree with the other review that says it really makes an enormous amount.
On what planet is this enough for one 8-inch layer cake? I thought the recipe looked disturbingly huge so I cut it in half. The halved recipe yielded so much frosting that I layered it on my cake about an inch thick and still had a full 2 cups left over. Do not make this whole recipe if you are just planning to frost one 8-inch cake. Seriously, does anyone at Martha Stewart ever test recipes before they are published? I find this kind of error distressingly common in MS recipes.