PowerArchiver 2006 supports the 256-bit AES encryption that WinZip added with version 9 (you'll still need the password, of course). If security is paramount, PowerArchiver 2006 also includes AES-256, Blowfish-128, and Triple DES-128 encryption. Archives protected with the latter two methods are able to hide the names of files they contain; however, those archives also use PowerArchiver's own .pae file format, which can't be read by other programs.
While PowerArchiver 2006 creates a variety of archive types (.zip, bzip2, .tar, etc.), it uses the .7z file format at an "ultra" setting to achieve maximum compression. (The 7z format was originally developed for an open-source program called 7-Zip.)
Like every program we looked at, PowerArchiver 2006 can create multiple-volume .zip and .7z archives (split into multiple files of user-definable size).
PowerArchiver 2006 also offers some excellent extra features, including an easy-to-use automated file backup wizard and the ability to upload backups to an FTP server, all without leaving the program.
At $20 (as of 12/6/06), PowerArchiver 2006 offers more features than the respective $30, $29, and $25 entry-level versions of WinZip, WinRAR, and StuffIt. It's definitely an attractive option if you're looking for an archive tool that includes automated backup/FTP capabilities.
You can find the full review and performance details for this program, and its competitors, at our Top 5 Compression Utilities chart.