I constantly try different cheese combo's on pizza and have used many cheddars over the years. I have often commented that I feel that a lot of pizzerias add cheddar to their mozzarella as a way of amping up the flavor. Land o Lakes is a mild cheddar, as are the cheddars from Great Lakes Cheese. One "problem" (as some people see it, but not necessarily the way I see it) is that cheddar tends to "oil off" more than mozzarella, so you have to be conservative in it's use. Presently I prefer to blend mild provolone and fontina cheese with my mozzarella, but I will still use some cheddar on occasion. Another great cheese to blend with your mozz is cheese curds, the infancy stage of cheddar. Many cheeses work on pizza, I just try to stay away from extremely sharp cheeses as they ruin the taste for me.