There isn't anything wrong with Windows Phone that isn't theoretically fixable. The problem today, as I see it, is that while Windows Phone is equally good as the products from Apple, Google and BlackBerry in most respects, there is no "one thing" that makes a Windows Phone a must-have.
What should be Microsoft's strategy with Windows Phone now? Apart from the obvious "blocking and tackling" of trying to narrow the "app gap", it should acquire BlackBerry or at least offer a model with a BlackBerry-style keyboard. That's probably the easiest path to differentiation against Android and Apple.
At the time of submitting this article, the author was long GOOG, AAPL, BBRY, NOK and QCOM.