Summary: Set it and forget it. I installed this unit in a 4770k build with a radeon 5870 gpu. The system under max overclock of both the cpu and gpu can only generate 400 watts or so. With that said, typical idle usage sits around 75 watts and even at roughly 10% output i generally get around 80% efficiency. It produces no audible capacitor wine that I could detect with the fan in 0 rpm mode and my ear right on it.
Summary: I bought this to power two gpu's that I bought a couple months ago, and it is quiet, the fans rarely turn on and when they do they are pretty quiet. There are lots of options for cables, and I really appreciated that. Would recommend. However, because of my increasing power needs, I think I'll be moving to the AX1200i. Either way, having a platinum rated PSU is possibly the best thing you can do. After that, giving it 220 volt power is the only thing better to do.
Summary: Having built my own computers for a number of years, I have long been convinced of the necessity for a quality power supply. This is the first non-Antec power supply I have purchased in quite a while and it has convinced me of Corsair's quality. I will continue to use their power supplies in the future.
Summary: Great/flexible Modular cables make for easy cable management. Plenty of power and this is the lowest of the wattage for the AX series. Running 6 4TB Sata Drives, raid card, Fans, SSDs, MB, GTX 570 and 3770K with plenty of power to spare!
Summary: Dead on Arrival. Corsair has the worst ticketing system for RMA. It takes around 1-2 business days for you to simply talk to someone through their technical support site. When they do, they message you with a question. You message back, and have to wait another day for a reply. This went back and forth. The RMA process still isn't complete yet. It's been 7 days.
Summary: the fan doesn't respond to commands to speed up or slow down and makes an insane racket. i had planned on this for my dask tower, but after 2 days of the mind blowing noise i moved it to a server and walked away. it's a great product, wonderful, steady power, but the fan issue is enough to kill it.