They may be a fad. But it doesn't matter to me. I love several that I've played. I have a Tom Bills with a side soundhole, none on the top. It's a loud beast for the player and certainly loud enough for the audience. I've also played a classical by Randy Reynolds with an offset hole in the upper bout top. It blew my socks off. I think they are great. Sort of different take on a port. The main idea is to put the soundhole where there is less energy being generated by the top, to free up the area where there is more energy potential. Controversial topic, and some don't buy it. Some think they are ugly. These people wouldn't own one. I would own several.
My Bills:
Randy Reynolds' Concert Grand classical.