News that usage of Internet Explorer 6 has now fallen below that of Internet Explorer 8 (despite the latter's bizarre vomiting ads) is interesting because it is boring: it was inevitable at some point. But it possesses huge symbolic importance.
For it was Internet Explorer 6, released in 2001, but only replaced by Internet Explorer 7 in 2006, that essentially drove the rise of Firefox. IE6 had become so old-fashioned and unfit for the purpose that many people were delighted to discover the power of the upstart challenger, indifferent to or ignorant of the fact that it was open source: they chose it because it was so much better.
That IE8 has finally overtaken IE6 means that Firefox has changed the browser landscape to such an extent that even the most resistant to change are finally shifting to a modern browser. In some measure that's down to the fact that Firefox has continued to move forward in this space, making IE6 look increasingly prehistoric in its approach. Whatever the reason, it's good news – for everyone. I imagine that the huge installed based of IE6 has been responsible for enabling much of the worst Windows malware to propagate and inflict itself on the world.
The other thing to note is that just as IE6's demise was bound to happen, so, too, is the attainment of the magic 50% market share by Firefox. It's already there in a number of countries, and even in backwaters like the UK, the figure is creeping up. It's just a matter of time.