I'm not sure that you would know. This is my user agent string:
Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; InfoPath.2; .NET4.0C; .NET4.0E)
...running the current version of Opera. Most other people I know that use opera do the same thing to get around silly sites that won't even try to display their content.