AnandTech has published a review of the 1000W Corsair HX1000W power supply:
Set the sails, Corsair is coming. It took a long time for Corsair to get on track with higher performing power supplies, as until now the company only offered up to 750W of power with their TX series. Following in the footsteps of the successful HX series, Corsair now brings the HX1000W to market, delivering the expected 1000W of power as the name suggests,. The HX series consisted of the 520W and 620W until now, whilst the step between 620W and 1000W is covered by the TX750W. Corsair focused on bringing in one new high performance power supply, instead of several in-between sizes like an 800W or 900W. That's sensible, as it's difficult to imagine situations where 750W is not enough but 1000W is too much. Also of note is that the Corsair HX1000W is the first 1000W power to receive NVIDIAs Triple-SLI certification, as previously NVIDIA only certified 1200W+ power supply for Triple-SLI.
Check it out over here. The reviewer says the unit has the best stability they've experienced so far, the output quality of the HX1000W is great and the efficiency is well over 80%. He also writes the noise was lower than he expected and praises Corsair for giving a 5-year warranty on the HX1000W.