Nice tutorial, thanks.

It may be useful to note, that also broadband access users profit from zipped content. Their browsing experience is getting snappier as well.

The reason is as follows:

Gzipped content is smaller. It is likely it fits into fewer tcp packages than non-zipped content. So you save packages but spend more time unzipping the content. When unzipping is faster then the delay until the next tcp package arrives, then you gain time and browsing becomes faster. With today's computers, unzipping is generally faster than the network delay, so zipping web content pays almost all the time for the browser.

As pointed out by Falko, on the serverside, you trade of CPU for memory disguised as network usage. This means, that non-zipped content means more tcp packages, means longer connection to the user, means using an apache process/thread for a longer time, means more processes forked, means more memory used.

In most webserver situations you have lots of CPU, but not enough memory. That's why zipping content helps in most situations on the server too.