I got this to open a .sit file -- I didn't want any more of that stuffit stuff for me on my hard drive.

The first time I ran it it put up a preferences window with a checkbox for each of the formats it could handle. I checked the checkbox for .sit files.

Then when I opened my .sit file it went directly into The Unarchiver and it opened it with no problem.

So, for my simple use, the app could not have been easier or worked better.