As mentioned above a variety of factors play in when I'm scoring. Stories that make it clear that the author was paying no attention to grammar or spelling start at a three and go down, because it really isn't hard to capitalize an "I" or hit the spell-check button.
I will also mark down if it is cliche ridden, unbelievable, or just frankly stupid.
I will give a minimum of four for stories that are well written, regardless of whether or not I'm all that into it, with fives reserved for stories that just plain do it for me and are a pleasure to read. The ultimate compliment I can pay to a writer I enjoy is to follow them, because it takes a lot to get me to sign up for emails every time that person posts something new.