I've just seen that there is quite interesting website where you can get statistics about browsers/platform/OSs usage: http://gs.statcounter.com/.
Just go there and have a look, it's very interesting. The only thing you might want to know is where do they get there data from ? Basically from there main function: providing stats over internet. See what they say: "Stats are based on aggregate data collected by StatCounter on a sample exceeding 4 billion pageviews per month collected from across the StatCounter network of more than 3 million websites. Stats are updated and made available every 4 hours, however are subject to quality assurance testing and revision for 7 days from publication."