From TUAW:

Impress Corporation of Japan is reporting that Apple now controls almost half the smartphone market in Japan with over 3 million iPhones sold to date. Keep in mind, it has taken the iPhone little more than a year to accomplish this.

Impress reasons that the major shift towards the iPhone is because of its ease of use and the Japanese App Store.

One of the predictions I distinctly remember an analyst making a the iPhone announcement launch was that it would reach Apple’s 1 percent of market share goal but it would have no impact in Japan, where the phones were so allegedly advanced.