There are many authors that I read that I think the stories are well conceived and written, I just HATED the story, I don't know how to vote.
I generally vote based on how I feel about a story. If it's got plot holes or major inconsistencies; but if I enjoy the story overall then i'll vote higher than if I didn't enjoy it. Of course it would get a higher score if it was more tightly written.
I tend to vote lower for stories that have poor spelling, wrong words used, missing words etc than ones that have issues with the plot as those things I find often detract more from the story (unless the plot holes are massive of course, or the characters really annoying or flat or unbelievable).
Likewise if I actually finish a story that is well written, technically & plot/character wise, but I didn't like it then I will vote much lower than if I had liked it.
However it's usually the case that if I don't like a story while reading it then I won't finish it, and I don't vote on things I don't finish.