The term is overused, but this seems to be smart, simple and high-impact, and I can well understand why the Dragons got excited. 

Customer inertia has long been a major factor in overpayment of energy bills and inefficiency, with incredible proportions not switching when their deals change. To create a "hands-off" system where that hassle is taken away is a superb idea. 

What is does do, however, is reduce the switching decision solely to price. Although this is, I'm sure, overwhelmingly the main factor behind a purchasing decision, it does ignore the opportunity to opt for 100% renewable energy tariffs, "vegan generation" (thanks Ecotricity), or supply companies providing local or social benefit (Bristol Energy, Robin Hood Energy).  

Supply companies will therefore need to work as hard even harder to differentiate their offerings and generate customer loyalty.  Look After My Bills may not be fior everyone, but I suspect it'll work for the majority.