Specific reasons why? I've had several Asrock boards (including one mini-ITX) in the last three years and they've all been just as well behaved as any other manufacturer. That doesn't mean trouble-free, just that Asus, MSI and Gigabyte all have their woes too... although it can depend heavily on the board model in question. Personally, I've had a poorer experience of MSI than the others, but they've all released a troublesome board or two over the years.
edit: I was eyeing up the Asrock H470 board myself a few days ago, but in the end decided I had better things to spend the money on.