As in the past antitrust case, won by the EC, there are two parts: one is the bundling IE with Windows and the other is the interoperability issue. As before, the bundling issue is less important because the real problem is interoperability, a word that Microsoft has always interpreted in a monopolist way: I do whatever I please, and I set ‘industry standards’ by myself convincing clients and partners to either follow me or be squashed.
There is little doubt that Internet Explorer doesn’t support W3C standards well as Safari/WebKit, Firefox and Opera do, but nonetheless many web application prefer to support the non-standard browser because of IE has 80% market share. So, the question whether Opera is right to complain to the antitrust authority is a clear yes. Opera made a tactical move to pressure the dominant gorilla and at the same time inform the public about the interoperability issue. If Opera really cares about interoperability it should also support the W3C to keep its power and resist against Nokia’s proposition to remove referent to patent-unencumbered OGG format from HTML5.
Update: Microsoft informed that internal builds of IE8 pass the ACID2 test