I bought this because I needed a flash diffuser for a Wedding. Given more time I would have made something similar myself, but I had other things to do. I don't think most Flash users should be without a product like this. If you know what your doing, or going for a specific look, you could do without, but other than that any flash user should have a product like this.
It works well, but I would hesitate to use it unless you have a top-of-the-line flash, as the loss of light can be too much for smaller flashes. When used on my smaller flashes, I find that recycle time can be painfully long since they have to work much harder with a diffuser on them.
BTW, For what it's worth I got my best photo of my black cat using this product.
Works very well. Requires using velcro on flash