Personally, the spelling issue doesn't bother me at all, and I sure as hell don't expect writers to change their habits just to suit a small vocal minority. I think that if you're that easily thrown out of a fic, you're just too tempermental a reader.

I do hear it a lot from all angles, though. I sat in a Harry Potter panel at a con a few years back and listened to a British woman tell us that unless we had a British BETA, we Americans had absolutely no business writing HP fanfic AT ALL. She wasn't really content with us using on-line guides either - had to be a real beta, or she wouldn't read it at all.