I have (heavily) touted, in the past, the use of free alternate compression programs, such as 7-Zip. The biggest complaint I get from my own users when I try get them to use it is the interface is too clunky. While I somewhat agree that it isn’t the nicest looking of interfaces, it certainly doesn’t suffer any usability flaws (in my opinion at least). If this sounds familiar, try taking a look at jZip.

jZip is built off of 7-Zip so it is fully compatible with all formats supported by 7-Zip. The big difference is the interface. The icons resemble Winzip and the file management paradigm is basically what Windows Explorer looks like. It doesn’t get any more basic than that.
So if you still have people waiting 30 seconds for Winzip’s nag screen to go away every time they open a zip file, see if you can get them onto jZip instead.