The real reason why Nokia chose Windows Phone 7

Choosing Windows Phone 7 as Nokia's primary smartphone strategy is  actually in line with their Symbian strategy. Nokia really had to find a replacement for Symbian as a smartphone OS. There is really not much more than can do about making a OS designed for a keypad friendly to a touchscreen. 

By 2011 this is what their line-up will look like by the 3rd quarter of the year:

• High end: WP7
• Mid Level/Entry Level Smartphone: Symbian S^3
• Feature Phone: Symbian S40

Technically, right now Nokia does not have a "high end" smartphone. The N8's price is really more mid-level and it competes against one year old Android in price point.

By 2012:

• High end: WP7
• Mid Level: WP7
• Entry Level Smartphone: Symbian S^3
• Feature Phone: Symbian S40

If Nokia had chosen Android, well they could, and would have to put it, on all their smartphones as soon as possible. If Nokia promoted Android as their premium product, it would promote all their competitors mid and entry level Androids. This kill all their mid-level Symbian's today. What would they do with their existing stocks. Sell them at fire sale prices?

Right now though. Unless there is no Apple iOS, Google Android or Microsoft WP7 option at the same price point. It does not make sense to buy a Symbian S^3 anymore.

Nokia may try to support it. Nokia will try to convince there is still a future in Symbian, but who will still build apps for it? Symbian S^3 is dead. Nokia will try to flog Symbian S^3 into the market until, WP7 can be feasibly sold at lower price points.

Besides, once they finish their Symbian stocks, they can always use Android in the lower end smart phones.