Quoting from [Kalai]:
A Windows Mobile device, the X1 features full QWERTY, a 3.2MP camera, 3-inch touchscreen at 800 X 480 resolution, Wi-Fi, 400 MB of internal storage and microSD support. Plus it’s ready for every frequency under the sun for Europe and the US.
From Press Release:
The frequencies it works on: (GSM/GPRS/EDGE 850/900/1800/1900 or UMTS/HSDPA/HSUPA 900/1700/1900/2100 MHz or UMTS/HSDPA/HSUPA 850/1700/1900/2100 MHz).
Today marked the launch of XPERIATM and a new era in mobile communications with the announcement of the XPERIA™ X1, a stand-out, arc slider phone from Sony Ericsson designed to address the growing need for a premium, converged mobile experience.
Source: http://www.topblogposts.com/2008/02/sony-eriscsson-xperia-x1/
Quoting from [Kalai]: