They have the two largest smartphone manufacturers outside of Apple and RIM, in HTC and Samsung.
Among the large manufacturers, all they are missing is Sony Ericsson and Motorola. And I believe only Motorola has hinted that they are Android only.
And Nokia is still larger (not for long) than #2 and #3 in terms of worldwide sales.
It is, WP7 marketplace already has around 15,000 apps and is growing faster than the iPhone and Android stores at a similar stage.