There have been many video reviews of the Fujitsu IS12T, but as they tend to be in Japanese this has been less than helpful to a western audience.
PC Watch have published a more text-heavy review of the OS, which is at least susceptible to machine translation.
From there we can gather that the reviewer found the battery life was amazing, thanks in part to its massive 1,460mAh battery, that the reviewer was impressed with the OS, and especially the integrated social networking and but did complain of the lack of support for GREE and mixi integration in the peopleâ€™s hub. ( GREE and mixi are social networking sites and are more popular than Facebook in Japan).
In the above video we see web page rendering being compared to the iPhone 4, and the reviewer notes both take about 8 seconds to render the page, and are equally smooth when it comes to pinch to zoom.
While the focus on iOS and Android are applications, the Au IS12T with Windows Phone 7.5 is different in nature with a focus on people. Naturally, the OS is a bigger feature than the actual phone itself, and is agnostic with support for both Windows and Mac OS X synchronization. In terms of hardware, the IS12T is somewhat mediocre, but still light and thin, waterproof and dustproof! It uses light materials suitable for the handset.
Windows Phone 7.5 itself, while still lacking applications and unfinished in parts, is despite this still a very attractive environment with its user-centric social networking.