Net Applications tracked iPhone usage since its launch.  Total web browsing on the iPhone has topped the web browsing on all Windows Mobile devices combined, their report shows. Their report is a listing of the top operating system versions in use.  It is not a measure of units sold, but the share of users browsing the Internet with the devices.  The iPhone has had a dramatic rise in usage share in its short time on the market 

In their report for November the iPhone had .09% market share and Windows Mobile had .06% share for the month.  Their report can be sorted by different variables and downloaded at their website.