There is some confusion about what this app actually does- I didnt know until I bought it.
Rather than add a flash to the iPhone camera ( which is what I was hoping for), it allows you to adjust the exposure lighter or darker.
It does a fairly good job & you can apply multiple times to increase the effect, however it lacks fine control. Adobes Photoshop iPhone app is a much better option for doing this (and lots more), although I dont remember the price for it (probably more).
Tian V about Camera Flash Deluxe