I recently hit this same problem myself, and found that it not only doesn't work with Safari, but also Chrome.
in reply to Apache2::UploadProgress & Safari bug status??
After much head-banging (and significant help from a co-worker), I did find a work-around.
Edit the file /extras/progress.js, and modify line 85 as follows:
- req.open('GET', url, Boolean(handleUploadProgressResults));
+ req.open('GET', url, false);
It appears that the call to handleUploadProgressResults will always return true in Chrome/Safari. No idea why, but modifying (hardcoding) this to false does get things working.