OK, so I am having the same problem with mine. I've got the 9C81 screen.
As far as I can tell it's related to temperature. It only happens if the computer has been asleep for a while. Even then it only happens if the ambient temperature is below about 70° F. I found that if I turn up the brightness to maximum (on battery) before closing the lid, the backlight will always turn on without the stripes upon waking the computer again. I guess when it is forced turn on at full-brightness it shocks it into turning on correctly. Since I started doing this trick, it hasn't failed. I know, I shouldn't have to do that but it's only a minor routine to get used to.
I really, really didn't want to return my MBP because this is the only problem with it. I didn't want to risk getting another MBP with more severe problems. Considering that this problem doesn't seem to be related to just one screen model, I'd say it's related to the backlight controller. Since it is temperature related in my case, I don't think that it is software related. I'll wait until a real solution is available. For now my workaround works for me.
Very Good Point!