I only use WinRar, it is easy to use, friendly interface, you can open zip, rar, ace, gz, tar, iso and Poser's (pzz,crz,ppz,....)!!!! You also can look/open what is inside zips.
And if you want to compress something you can do it into multiple volumes (.rar.part1, .rar.part2, part3.....), excellent for backups that don't fit in only one CD.
And I hate Winzip!!!!

Stupidity also evolves!