Works, but only with a little fiddling.
So on the upside: this works, and charging your phone “by magic” is exactly as cool as it sounds. It makes marginally longer to charge, but if you’ve got an S5 it’ll probably save you time in the long run because you don’t have to keep opening the waterproof seal at the bottom of your phone. Plus, this charger uses the Qi standard so it’ll be compatible with lots of other inductive-charging devices now and in the future.
Unfortunately I’ve found that it’s quite fussy about where exactly you have to place the phone in order to make contact. A centimetre or two out from the ideal spot and the phone keeps losing the connection and then regaining it, causing it to beep and the screen to flash (which isn’t much use if you’re trying to sleep!). The upper surface of the charging pad doesn’t have much grip and is convex in shape, so it’s very easy to knock your phone off the ideal spot, too. And while it’s reasonably price, it still feels a little cheap that it doesn’t come with a power supply of it’s own (you have to use the one that came with your phone).
All-in-all, I wouldn’t recommend this, even though it “works”: there are probably better devices out there.