Had to make a tweak to Tornado last week as we discovered that multipart mime file upload would not work correctly with Safari 3 after an upgrade to Leopard. The issue was that if Safari could not determine the mime type of what it was uploading, then it wouldn't bother sending a content-type: mime header. This was one of the things Tornado looked for to determine if a file followed. :-(
Detection rules are updated and Safari 3 now works.