To be fair this is not the only complaint about Black Screens on the 290/X.
Having said that if your not getting them with the card (untouched) then its not broken as such, thats not to say nothing is wrong with it, or the drivers, or a combination of that and the OS.
If its Black Screening (untouched) just send it back, if not, accept you didn't get a great one for tweaking, wait for improvements, or DSR if unimpressed.
I would agree, its always a lottery with overclocking, but it is possible its an OS, driver or utility that's causing the problem, at this early stage it looks like us the buyers are the ones who are going to have to trouble shoot and find what is causing it.
Out of all the threads I've seen regarding this I can't remember seeing one where people report the OS they are using, they mention drivers, bioses and overclocking utils but not the OS.