Most people haven't had a problem with the 300degree rails, but a few members said that they had trouble getting their authentic rails to seal (in response to Coz's "coming clean" post). Coz also claimed that this is the main reason he copied them. Then I read your post "I always wondered why the 300D rails didn't use o-rings" and that's why I came to that conclusion.
I hope my post didn't make it sound like 300degree's fuel rail is a bad product because that definately wasn't my intention.