Some of my colleagues are working on a project where bandwidth is massively limited (64k). One suggestion to increase application response time was to use MOD_GZIP (an open source compressor extension to Apache) to compress the outbound HTTP traffic. The only drawback is that MOD_GZIP is not supported by Oracle.
Since we are using Oracle Application Server, Web Cache achieves exactly the same by simply adding a compression rule to Web Cache for the URL Regular Expression /pls/apex/.*$
We noticed that without any compression of the HTTP outbound traffic, our test page took 30 seconds to fully render on a 64k link. Turning on compression reduced the rendering time to 7 seconds. Very impressive.
Navigating through an application with compression turned on was noticeably quicker than one without compression.
To test if your outbound HTTP traffic is compressed, I would grab the Live HTTP Headers extension to Firefox and you are looking for a line like: Content-Encoding: gzip in the outbound response.
I configured both APEX and Discoverer Viewer to use compression by following the metalink article: 452837.1