He who has imagination without learning, has wings and no feet.
Joseph Joubert
This sums up my opinions on this subject. Grammar and spelling is not the be all and end all to what makes a story. Yes, a great story with an interesting plot and characters that shows the wonderful mind the writer has is great. However, if it is full of spelling and grammar mistakes I must come to the conclusion that the writer doesn't care to really put the work into their story that it deserves. I do my very best to put honest effort into the thoughts behind the setting, the characters and the issue at play and I want to do that justice. I don't know everything but I know that if I am not sure on a grammar rule or spelling of a word I can and will look it up. It doesn't take long, I keep dictionary.com on my favorites bar and use it quite often. Writing isn't just getting your idea across to the reader. It requires more than just a great story, it requires that you put thought into how you present that idea. If you don't do the work on the basics then your story is likely to never really take off.