The application works for the most part, and the developer is quick to personally respond to questions.. but the application lacks some key features and usability that I think are essential in this type of application. I paid for the full featured program
My #1 peeve is this application lacks advanced direct comparison matching like SHA-1 or MD5. Almost every other duplicate checker and backup program for Mac, PC, Linux, etcetera use this methodology and through experience I just don't trust name, mod time, or CRC32 dup checking.
My #2 peeve is the overall usability of the application and trying to define what you want to check. It dumped down way too much and to me is annoying. I just want to point at a directory and say go check it for dups with these options. The basket system and being partially limited to pre-defined searches and custom labeling of tasks are annoying.
My #3, in the registered version I am using 1.4.5 there is a serious bug of if I say to check for dups in folder in my desktop it searches all directories above the directory I am trying to search as well unless I add it as a specific 'search path' on the side view. This could very easily lead to false positives or unintended deletions.

I crawled through it for a task I needed to complete very near term... but am on the search for a better product that applies the keep it simple and do it affective methodology. Thus I am being kind when I give it 3 Stars.