The best app so far :)
This is a Grate app. As a dslr photographer I highly recommend it. It worth to use it, you will find it easy to use. A two finger touch will just split the focus point from the light measuring point, a kind of fast spot meter. So I realized I could live without +/- correction button, which I use all the time on other cameras. Additionally the built in retouch filters match my stile of BW photography. Another grate feature that you can edit the image with a "curves" like function. That gives far-far more possibilities than would be a brightness/contrast combination button.
Conclusion: Take it, use it and you will never regret. This is FREE, and knows what you need to take grate images.