A number of people have commented that Firefox 4 download numbers are not really that impressive (even though they gave IE 9's launch downloads a serious thumping) and that what really matters is actual usage. So, with the help of data from StatCounter and NetApplications, I've prepared a little chart that shows Firefox 4 usage also trouncing IE 9's solidly.
As you can see from the chart, Firefox 4's release kicked off with considerably more excitement and momentum. IE 9's release, which was backed by one of Microsoft's biggest launch marketing campaigns in recent history, had a comparatively weak showing.
So what explains this disparity? It's you all. It's every one of you that downloaded Firefox 4, found it to be awesome, and told all of your friends and family about it. No ad campaign from Microsoft can top that. Keep spreading the word. Firefox answers to no one but you!