It packs down small and is light, so fit well in my bag or even a large pocket. It is very useful for close up work, for example when photographing spring flowers in a wood where light can be awkward. I guess it could be useful for impromptu portraits in the field, but lets be honest its a bit small for real studio work.
Very good for the price (feels like it will last, I've only had it a couple of months though) and useful for macro work of wildflowers etc. And a cheap way to make your photos better.