Ok well, don't be too worried about it. Sometimes it's a hit and miss with certain motherboards....more likely than not your motherboard should be fine.
I've read a few threads where their Asrock E4G3 is completely stable - and OC's well. But like I said - it can be a hit and miss with these "cheaper" type of motherboards.
If problems do arise once you get it...well you could probably just ask someone here for help.
I have the extreme3 version of it. Runs completely stable with 4.5Ghz aircooled 2500k and dual 560Tis. Pretty squishy 'board' though (literally). Have to be careful while pressing it while installation, I almost managed to break the edge 😛
As perfectblue mentioned - apparently some of those asrock boards are a little thin (literally). Some will be thicker on one side - and skinnier on the other side.
Just be very careful when mounting your motherboard not to snap it.