I have an ASRock running my 775 Core 2 Duo as a server at the moment, but it used to be my gaming computer.
I had no issues with it, other than it had a VIA chipset that didn't overclock all that well (probably due to the amazing flexibility that board had). Had it not been able to run a Socket 775 on either DDR or DDR2, AND be able to run an AGP card and/or a PCI-E card (amazing set-up for the upgrade path I was on), I probably wouldn't have picked it. It didn't have solid state capacitors, and was just generally a cheap board.
Some of their higher-end stuff is supposedly not bad, one of the biggest things I look for personally is solid state capacitors, as failing capacitors are usually the cause of premature motherboard deaths.