The app does a pretty good job of isolating the subject before applying the blur, and the two edit tools are useful to tweak the “coverage” of the to-be-blurred area. The problem is the sharpness “fall-off” from the subject’s sharp edge to blur should be more gradual, not so abrupt from sharp to blur, regardless of the amount of blur setting.
The effect looks its best if the amount slider is used minimally, and avoiding a heavy-handed max blur approach. In my particular image test, I needed an “appropriate amount” of maximum blur applied to background objects of varying degrees of distance from the subject, but the end result looked exaggerated and “obvious” as the fall-off went abruptly from sharp to max blur over the entire image. Everything was the same level of blur.
To real life the “depth of field” of wide aperture lenses, the transition is very subtle/gradual, going from sharpness to blur in front and in back of the subject, a very difficult effect to mimic in post processing.
Another suggestion, making the app Universal to facilitate better edits using an iPad would be an improvement. The app works OK on the iPad, but there is a lot of wasted screen real estate.
A very good effort that will work pretty well for some images if used sparingly, but could use additional improvements.