This is how I trade currencies, usually a Yen pair on a 30min timeframe. It does work and money can be made, but it is a lot less profitable then they claim (on the Yen pairs I trade). Generally, a very outsized event can erase quite a lot of gains. Even smaller ones can make you give back a bit (such as NY ebola news or surprise BoJ news). Over time those commissions/fees add up. Still, over time I would bet they could be profitable on this strategy on some timeframe. Of course, just profitability is a very different claim than their own.
