Six months ago, Nokia's stock was selling around $6. It's now under $1.80. That appears to be a fair proxy for the market's view of the viability of Windows Phone.
http://finance.yahoo.com/q/bc?s=NOK+Basic+Chart&t=1y
Nokia's Chairman is now saying they have a backup plan if WP "fails to live up to expectations" (most are guessing Android). Nokia had been vigorously denying they had a backup plan.