In current channel movement (as of August), rather than installed base, the numbers are (http://www.redmondpie.com/android-is-now-the-number-1-selling-smartphone-os-in-united-states/):

Android: 33%
RIM: 28%
iPhone: 22%

That's 83% of movement in the channel going to non-Microsoft. WinMo7 has a difficult row to hoe.

The good news is that, with the ability to write MonoTouch .Net apps for Android and the iPhone, WinMo7's success or failure should not impact .Net developers.

Hank

>Despite all it's hype, last I saw, the iPhone has 17% of the market. With Android available from all carriers and multiple hand set manufacturers, it's easy to see why it will have such a large market share. The only other player in the US will be Microsoft. We'll see what they do with WinPhone7. Palm will be an albatross carried by HP.
>
>>At present the mobile phone market is dominated by mass-market cheapy handsets, including in the US, so overall figures for smartphones appear lower if you look at all phones or even all data phones. If you limit yourself to smartphones, you're more than likely correct about Android- certainly Gartner agrees that Android will be the one in the US by the end of this year.