The Windows Phone 7 is due out soon and there is much speculation about it. Personally I think Microsoft is a bit late to the party and they are taking some awkward steps to get there.
The most recent news from Microsoft was that they won't be supporting CDMA phone lines until 2011. So, in the US, that means no Sprint or Verizon.
I'm sorry... Microsoft doesn't have unlimited resources? Yes they do... this is a cost saving choice, but they have the money to do this right.
Split rollouts like this may have worked for Apple since they started the consumer based smart phone revolution. However, choosing AT&T and T-Mobile in the US over Verizon and Sprint just seems.... fucking stupid.