The biggest mistake was mine in that I used half sharp cheddar cheese and half monterey jack. I should have used all sharp cheddar cheese as the combination had so little flavor that the casserole tasted like flour and milk.
To make the sauce richer I used 3 cups of low-fat half and half and eliminated the water but the casserole was watery on the bottom.
With the right mixture of ingredients hopefully this recipe could be tasty. Don't think I want to risk it again, though.