I've been dealing with browser-based large file uploads, which means dealing with lots of browser-specific issues.
Fortunately, things are getting better, especially for the webkit-based browsers. Firefox still has some issues, and I check https://bugzilla.mozilla.org/show_bug.cgi?id=678648 pretty regularly. Just today this bug, which was filed in 2003, changed from Status = NEW to Status = ASSIGNED.
Today is a good day.