From his conclusions:
I remain cautiously optimistic that Windows Phone will catch on. For one thing, Microsoft can afford to be patient with it--and the world's leading software company really can't afford to abandon the smartphone software market.
More important, Windows Phone 7.5 is a fine operating system that deserves to be successful. Sooner or later, good products usually do okay. If Windows Phone doesn't, it might be a sign that the dynamics of the smartphone business aren't going to let anything that isn't iOS or Android do well anytime soon.