I would have to say that the phrase "most advanced program ..." in the product description is certainly an exaggeration. This utility software is indeed useful in finding certain kinds of duplicates, based on such things as dates file name and type as well as creation and modification date, as expected, but because it doesn't calculate the checksum for files, there is no way to find files with the exact same content but different file name or dates, which frequently happens with identical files that have been downloaded on different dates and even had their name changed without actual content. The only way I could confidently delete duplicates with this application is if all of the details (dates, size, creator, type, etc.) matched when their is no checksum to really make sure, and even then, chances are that you're missing out on other duplicates for which any of these details have changed without affecting content.

Strangely, the product description also mentions comparison by "content," but there is nothing in the interface or accompanying documentation to indicate that this is true.

To find true duplicates, regardless of file name or differing dates, zsDuplicateHunter appears to be the only software available for the Mac that does checksum calculations when searching for duplicates.

However, because zsDuplicateHunter does not scan metadata, this application still has some important use. Also, being Mac OS X native, this utility is much quicker than zsDuplicateHunter, by far. If you don't mind paying for two applications, use this one first to quickly find files with identical file names and dates, etc., and then use zsDuplicateHunter to find all the rest. Afterwards, you can return to Doublet Scan for a third session to find music based on metadata that hasn't been eliminated by the previous two methods.

Actually, you can preface all this by using OmniDiskSweeper to first get rid on non-duplicate large files that you no longer use, as it is much quicker than trying to search directories with the Finder.

If Doublet Scan did add the quick Adler32 and CRC32 algorithms and even the slower but more accurate MD5 and SHA-x algorithms for calculating checksums as one of the search criteria independent or in conjunction with the other criteria, this would become the one supreme duplicate-searching/deletion utilities for OS X, requiring no others.

The reported lack of tech support is definitely a concern, but I can sympathize, knowing that the developer is not a native English speaker. Although I speak, read, and write Japanese and Chinese, it is still a pain to have to use them in correspondence, even when one is receiving money for it, so I'm sure it's the same for the Italian speaking developers having to use English.