Depends on your goals.

That article is nearly a year old. Newer figures show market share of Windows phones has leveled off, meaning it's no longer declining. You'll see it go up over the next year.

know which must-have apps are missing from WP7 so I can write them and cash in.
>
>It would be a bad invest. You know WP7 has the smallest market. :)
>
>http://blogs.computerworld.com/17727/new_sales_figures_show_windows_phone_7_sales_go_from_bad_to_worse