Personally, I think grammar and structure DO matter. They serve a real purpose, after all, not just to let English professors fit in at dinner parties -- they allow flow and clarity. Truly bad grammar -- to the point of illegible sentences -- make a story horrible no matter how good the idea and word choice is. I weight it not as its own feature, but how it affects the story overall. If I didn't enjoy the work because of the bad grammar, then the work wasn't enjoyable, ya know? I also won't give a 10 to a story that still needs a basic spell check