i also have this question. Just searched the forum and found this thread.
It seems the current situation is rather not optimal. Google probably should do something about it.
For now i think i'll just rely on plain old web server log.
here's some detail for any who might be interseted.
• according to the help page, one needs to add js code for onClick, but that doesn't track people who right click and use the contextual menu to download. This is how most people download zip/pdf etc files anyway.
• adding js code is a pain, and gets a bit complex. For example, according to the help page http://google.com/support/analytics/bin/answer.py?answer=55529 , it mentions _setAllowLinker _trackTrans() which isn't in the code, nor explaining what that is. And it also mentioned about the the order of the code should appear. I'm famiilar with js so i know the reason about the order but that's getting complex.
• For example, this means i have to add the code to every page i want to track a download file. (i have about few hundred of such download files on my site.)
• the sample code embedded js into the link, which is not clean method, may not work with many site gen systems. For my site, js is not allowed to be embedded in the html page. Rather, tag are given id or class, and js use the id to add any interactive behavior. So, this means, there's gonna be quite some non-trivial coding to get this functionality out of GA, in contrast of GA's ease of use by simple GUI.
but anyway, Google Analytics is great. The above just some extra points for thought. Thanks.
Xah ∑ http://xahlee.org/ ☄