Well, in my short, 6 month OCS experience, I saw quite a few prior enlisted DOR. The reason? The vast majority (of the ones that quit), let OCS screw with their heads on a very deep level.
They had the "This is B.S. to get treated this way, I was coming up on chief, and now i'm being treated like I don't know squat about the Navy.. blah blah blah" attitude.
There were two types of priors that went through OCS (in my experience)... Either they greatly excelled at everything and let their enlisted experience play a fundamental role in helping themselves and the class, or the second type; those that let a poor "I'm too good for this crap" attitude take them down.
It's almost as if the ones (that had the bad attitude) didn't know how much of a mindf*ck OCS really was prior to arriving... As if they weren't prepared or didn't know what to expect.
I think that as a prior, if you can avoid the attitude pitfall and go out of your way to help others in the class (from everything like how to properly make a rack, to convincing them that OCS isn't at all like the "Real Navy"), you will probably rise to the top of your class.