Here's an article comparing the use of Gary Fong's light sphere and a simple piece of paper.
http://www.friedmanarchives.com/Writ...user/index.htm
For those that like to skip the article and go right to the conlusion..
"Okay, so let's recap... The paper diffuser produces results that are at least equal to the best that the Gary Fong diffuser can produce. Not only does the paper version cost considerably less, but it helps the flash's batteries last longer by not diverting the flash's output behind the photographer. And I was unable to get results that equaled the tungsten balancing examples on Gary Fong's website (http://store.garyfonginc.com).
Conclusion: I'll continue to use my tried and true paper diffuser."
I currently use an omni-bounce but may have to give the paper a try. I've always suspected there wasn't a whole lot of difference, but it's nice to see the side by side comparisons in that article.