Works well and is very portable, so makes s useful addition to a photographer's kit bag, but seems over-priced for a simple lump of plastic. It seems hard to believe that it works significantly better than some of the much cheaper, unbranded versions.
I'd certainly recommend buying this or an equivalent, but if possible buy other types of diffuser as well, perhaps including a flash umbrella for portraits. Then experiment with them, including simple ceiling/wall bounce, and choose the technique that best suits the circumstances and subject.