I've recently tried the upload progress on apache/mod_php 5.5.8, and... it doesn't work with the built-in (new) upload_progress status :(. Talk about code-rot..
The same setup works in an older version of 5.5. Looks like there might some difference in buffering or concurrence model maybe within apache!? but I gave up in trying to understand. I decided to remove the server-side support for upload-progress. It's very difficult to support cross-browser especially for older browsers, due to the need of a separate iframe just to be able to have some JS running while the main frame is blocked (this was done before web workers didn't exist). Not to mention that it doesn't work with php_cgi/fcgi aud suPHP, which are increasingly common. I only use fcgid myself. It's all very kludgy. I think times are mature to use a client-side status indicator, which is something you can do with XHR objects since a couple of years. On yeah, and it works on any PHP setup. It's the way it *should* be, and it's the way the python clients do it. It's in the master branch as of now. Older browsers that used to work (IE6 up to 8 - I think) though won't get upload status. Fair enough? I tested with FF and Chrome, and it works like a charm. I'd be curious to know about your experience. I have no way to test IE.
