I have been using this power supply for a while now and in general I am very happy with the performance. I run an i5 2500k (stock) and a GTX 780Ti and the power supply was obviously good enough. My system consumed about 130w when idle at an efficiency of 80% and about 340W under load at an efficiency of 90%. This power supply is definitely an overkill for my usage. I would recommend it to someone who is looking for a dual GPU configuration or someone looking to do some pretty heavy overclocking on both the CPU and GPU. Otherwise a 650W power supply would be better.
One interesting thing I noticed is that it plays well with my APC UPS. A lot of people face this problem where their UPS has compatibility issues with power supplies with active power factor correction. I am not too sure as to the root cause of that issue, people say its because the UPS is not a pure sine wave one, but I have generally found it to be a hit and miss. It would work fine at time and fail other times. The RM850i did not seem to have any such issue, there were plenty of power cuts during my gaming session and the system worked every time.