I don't have a beta myself, largely because my fandom pieces are not in wildly popular fandoms and I do want someone who gets the 'verse in which I dabble. My original works, well, I have no excuse there other than not really knowing anyone I'd pester to beta for me. But I do also welcome concrit and delight in having someone point out where I can improve.
I have an inner Grammar Bitch who is relentless in terms of pointing out errors in punctuation, and who has made me twitch for years when I write dialogue that is not grammatically impeccable. Honestly, we aren't all known for flawless exposition all the time, and dialogue can sound stilted if you force the issue. I have manuscripts that will never get out of first draft if I don't reign in my tyrannical inner editor. I'm overly critical of myself, and the fact that I hit the publish button at all is amazing.
There should be a fine line between my obsessive self criticism and the blithe disregard for convention that triggered this thread. It would be refreshing, anyway, given that a great many of the people who can't be bothered to try and clean up grammar and punctuation errors are the same people who are upset by the lack of reviews on their stories.