Long Zheng: If one of the most compelling features of the iPhone are the third-party applications then its a sad fact for Microsoft since Windows Mobile has supported third-party applications since the last ice age.
Side by side, theres an impressive 18,000 applications (hopefully at least a 1:5 gem-to-crap ratio) for Windows Mobile compared to just over 2,000 for the iPhone. The exception being theres only one iPhone marketplace and about a bazillion WM marketplaces. Personally Ive avoided purchasing any WM applications because of this.