Source: http://gizmodo.com/this-extra-lens-is-like-a-megaphone-for-your-dslrs-pop-1325596701
It might occasionally come in handy as a bit of fill light for a shot, but your DSRL's pop-up flash is a poor substitute for a dedicated flash perched atop your camera. It makes sense why it sucks; it's designed to be small and compact enough to fold away. But with Rogue's Safari Flash Booster added to the mix, all of a sudden your DSLR's pop-up flash isn't so crappy any more.