It works, but I find the increased gap from the rubber case both causes the phone to heat up and it takes FOREVER for it to charge!
I had my phone for a 2 weeks before I received my otter-box and had the charge pad the whole time. Before it would charge just as fast as plugging it in but now in the time it takes for the phone to charge on a wall charger it gets maybe 30-50% on the pad. Honestly I would say it works but you will probably find it more convenient to undo the bottom plug and use the charger than spend 2-3x as long waiting for it to finish charging.
But if you do want to, the heat from the pad is no more than using the phone under heavy load, nothing to be alarmed about.