Yeah, it's a cool app, it offers better IQ out of the phone compared to the standard iPhone app, and it also gives a bit more control over certain aspects of exposure (+ the different film modes etc mentioned by PAul). I was hoping it would actually allow you to set the shutter and ISO yourself, which unless I missed something you can't do (you can however compose a scene that gives you the values you were looking for, and then lock focus and/or exposure from there). Night mode is also cool, it allows a shutter speed up to 1 second which I don't think the normal camera app does.

The controls are a bit fiddly but they work. The built-in help file is handy too, because there are quite a few options to fiddle with...

Full quality TIFFs are about 10MB, compared to about 2.5MB for the HQ JPEG out of the standard camera app.