This article in the NY Times says that iPhones account for a huge amount of mobile Web browsing. Looking at stats for my sites, I see the same thing. Roll in the iPod Touch and there's no contest. Various flavors of the Windows Mobile OS combined can't touch the Apple stuff.
I guess the thing that surprises me about this whole iPhone affair is that it's the first time that Apple jumped into a market they not only did no own or have a presence in, but it's a very mature market. They managed to just show up and have impact, which is pretty amazing.
To me this seems like a "well duh" type moment. sure there were browsers before it on almost all mobile phones (including WinMo) but none of them came anywhere close to emulating the desktop experience until the iPhone came out. I'm sure if pocket IE at least displayed a website as if you were sitting at a computer (like their DeepFish browser did) you would see a much bigger WinMo group. Personally, I only will use my WinMo device to browse the web when there is no other option available.
Its amazing to me that Windows Mobile never got this right.