I mean overall EVGA mobos, not only Dark series. In general problems with BIOS, problems with memory support and OC, some weird stability issues. Pretty much the same issues, mostly related to BIOS, were repeating in most EVGA motherboards since I remember. Good OC results were mostly on special BIOS releases used by overclockers related to EVGA like Vince. I don't think anyone else had really good results on these boards. You can check even our frontpage reviews. I remember that with last mobo were the same problems because of not so good BIOS.
This is also one of the main reasons why you don't see EVGA mobos in competitive OC benching. Even Vince who works in EVGA, multiple times used competitive motherboards if he wanted to break some records. If lower clock but more CPU cores are better option then he always uses EVGA mobos, but many of his results are not on retail products. Many are additionally modified for extreme benching and the same is with graphics cards.