Customers most agreed on the following attributes:
I usually try not to use a flash so that I can get a natural look in my photos. However, there are times that I do need a flash, that is when I use the Omni-Bounce to get an even fill of the suject and background in a dark or uneven lighting situation.
This diffuser is not as "custom fit" as the manufacturer might have you believe. It fits perfectly on about half a dozen strobes, and for about four other models (including my Sigma) the instructions recommend stretching the sides. This makes it very tight, it still takes me about half a minute to put on or remove. Exposure is fine TTL, or for ADI dial +1.3 or +1.7 flash compensation. Instructions say it reduces the range of your flash by 2.5x, which still leaves my Sigma with plenty of range.
I needed something to soften the harshness of the flash blast. And this foots the bill. It also replaces a lost one from a number of years ago.
The Sto-Fen Omni-Bounce by Sto-Fen permits me to soften the illumination in a very pleasing fashion for portraits. In addition it works wonders with macro-photography.