The FCC approved Sony Ericsson's Xperia X1 for release U.S. ten days ago. Today, you can download and peruse the full 26-page user guide for the one of the most highly-anticipated of the so-called iPhone killers.

So, if the Xperia X1 is on your must-have list, you can get more closely acquainted with your future bundle of smartphone joy now. Check it out here.

According to the FCC documentation, the Xperia X1 that'll ship here will only sport a 3G band suitable for AT&T's high-speed cellular-wireless data network. T-Mobile users, should there ever be any, will have to make do with the far slower EDGE technology.

At the CTIA Wireless Show last month, Sony Ericsson said the Xperia X1 would ship in the UK, Germany and Sweden this fall. Sony Ericsson said availability dates for North America, China, Australia and Russia would be announced in the coming months, however.

Sony Ericsson also released a software development kit (SDK) to allow developers to try their hand at building Xperia X1 Panels and applications in September. For the Xperia X1, Sony Ericsson developed a proprietary panel interface to run on top of Windows Mobile 6.1.

The Panels are lightweight applications that extend the phone's 'Today Screen' API to provide a fully customizable user interface on the XPERIA X1. The SDK will be available for free.

In addition to Windows Mobile, the Xperia X1 sports a unique arc slider design. So when you slide up the smartphone's high-resolution 3-inch, WVGA (840 x 480-pixel) touch screen, a wide QWERTY thumb-keyboard is revealed.

For more on the Xperia X1, see the articles below.