I'll have to test to be sure you still get streaming. It depends how the browsers handle xhr2 events with regard to gzip'd http. I /think/ it'll be fine but I need to check to be sure. Eg, with gzip on you still get progressive html rendering.
<?
echo 'Hey<br>';
flush();
ob_flush();
sleep(20);
echo 'Bye';
?>
Besides, even if you manage to stream it, I imagine inflating partially received content is not trivial for the browser.