I wouldn't be surprised if some sighted users turn on the screen reader to get the 'worse' (read: superior) user experience. In some cases, the screen reader supported experience would be faster, easier to use, and more reliable.
It might well be superior when released, but will it continue to support everything, or will it sit around with no updates and miss out on new features, or simply stop working and have no one notice?
In large, the reason the screen reader versions would exist is the threat of lawsuits due to the ADA. I work professionally in this realm and accessibility is a huge part of our development and QA process. A release doesn't go out unless thoroughly tested for accessibility. I presume that would just map on to the screenreader site forks.
