Asrock, may be fine, but there are not just Asus attempt to sell lower priced motherboards to retail. They were supposed to be of worse quality, and they were supposed to not besmirch the Asus name, that is why they sell them under a new name, so if they suck it won't hurt Asus' reputation.
However this doesn't mean they will be bad, simply that usuing lower quality components might mean worse overclocking, or things like that...so in other words they will work fine, but maybe not as well as an Asus board at the edge of the envelope.