Opera is secretive about its own non-compliance
It seems to me that before demanding from Microsoft to be more standards compliant, Opera should learn to be more open about its own non-compliance.
Opera keeps in secret their browser's bugs. You cannot search for a bug in Opera's bug tracking system to see if it is already reported, and if you report a bug they do not even care to inform if it is reviewed, confirmed, found duplicate or fixed.
There is a forum thread about it: http://my.opera.com/community/forums/topic.dml?id=222870&t=1202656953&page=1#comment2445288