As far as I have seen, those Gigabytes are from a relatively new to psu OEM MEIC (they usually make power adapters) but is seriously decent. They supposedly rank with the Corsair RMx crowd, with the bigger brother (AP-850w) ranking with the Corsair HX crowd in the Platinum range.
Jon and Oklahoma Wolfe have retired from doing the indepth reviews, so has Gabriel Torres for all intents and purposes. That leaves Aris (he writes for several sites including Tom's and kitguru) as pretty much it when it comes to a psu review. Aris says they are quite good, well built, well designed and more than he expected from a newcomer OEM.
I'd not be adverse to using one if there weren't alternatives handy.