This Survey of Large Browser Uploads has some interesting information regarding the HTML5 upload spec and what modern browsers are able to handle in regards to tackling a file over a gigabyte. I've been spending a lot of time in the Plupload Forums trying to track down the best methods for each browser to be able to handle such large sizes (without using Java). Turns out, it's one those areas where browsers still need a decent amount of work but we're making progress.