More than a few people have been successful. I don't know how many are chronic. It is a rough go, though, because "headache" conditions generally aren't included as a disability category. I think in most of the successful cases there was an original denial of the claim followed by at least one appeal. The "good" part is that you don't pay the lawyer unless you win (except for fees for making copies, etc.), but that's also potentially a "bad" part, in that the attorney doesn't have a strong incentive to work on a case that's got a low chance of success. I remember a couple of people saying that it was better working with a local lawyer than with a lawyer from one of the big national disability firms. And I remember someone saying that unless you have a gigantic file of doctor visits and medications tried, you probably shouldn't bother. You can put the word disability in the search bar (top right of every page), or some other relevant search term, and see quite a bit for yourself.