StuffIt Expander is a file compression and expansion utility that can handle a number of different file archive formats. It's a free app available from the App Store and several other Web sites, and it installs quickly.
StuffIt Expander supports a number of file formats, including ZIP, ZIPX, 7ZX, RAR, and TAR. The StuffIt Expander interface is clean, allowing you to create archives by the usual drag-and-drop method or by menu actions. Clicking on an archive file can unpack that archive. You can add password protection to your ZIP files. There is a registration nag that appears with StuffIt Expander, and while you don't need to register to use the tool, the nags will get annoying as time goes by.
We tested StuffIt Expander on a number of archive files created by several methods on different machines. While the app worked fine with ZIP and ZIPX files, we did have occasional problems with RAR files, some of which StuffIt Expander simply couldn't open properly. Whether this will be fixed shortly or not remains to be seen. Since Mac OS X includes an Archive utility, the real reason users would want a supplemental tool is for RAR and other archives not supported by the included Archive app. Unfortunately, because of these problems opening RAR files, we uninstalled this app.
Editors' note: This is a review of the trial version of Stuffit Expander 2011.15.0.4.