Not just hype. It's an excellent way to build a house. They're heavy, so it's only economically feasible if there's a manufacturer nearby, or delivery will be too much. The reason we use wood so much is that wood has always been cheap and easy to work with. But a house made of AAC will be sturdier and the "thermal mass" built in keeps the house's temperature regulated. This is especially useful in areas with hot days and cool nights.