When I've worked events with a Gary Fong Lightsphere mounted over my flash, I've had people ask me if that was Tupperware on my camera. Well, over at ImprovePhotography.com, they tested real tupperware against the $50 modifier in the article titled, Gary Fong Lightsphere vs Tupperware.
And the conclusion? "After my testing, I found that there was absolutely no difference in my opinion in the quality of the light produced by the tupperware in comparison to the quality of light produced by the Lightsphere."
If you go on to read the article comments, however, many readers say that the convenience of the Lightsphere compared to a DIY rig makes up for the price. I can see that.
I mention the Lightsphere in the free movie "Understanding light modifier types and their use" in my lynda.com title, Off Camera Flash. I think it's a convenient modifier in fast-paced situations such as wedding receptions. I look odd enough with the Lightsphere. Imagine if I showed up in my suit and tie with a hunk of Tupperware attached to my camera.
But I love the point that ImprovePhotography makes. It's a fun read if you have a moment.