Happy owner of an AsRock Z77 Pro4-M here. Followed AsRock closely through Sandy generation and read many reviews of multiple IVB AsRock mobos before purchasing. Like others have said, I wouldn't worry about it.
Main: i5-3570K, ASRock Z77 Pro4-M, Asus GTX660 TOP, 120 GB Vertex 3 Max IOPS, 2 TB Samsung EcoGreen F4, 8GB 1600MHz G.Skill @1.25V, Silverstone PS07B
HTPC: A8-5600K, MSI FM2-A75IA-E53, 4TB Seagate SSHD, 8GB 1866MHz G.Skill, Hand-Built Wood Case