Over at SonyStyle.com, Sony is accepting pre-orders for the X2a (only $599.99) and is noting expected availability as on or about April 29, 2010.
The X2a is a sliding keyboard styled Windows Phone running Windows Mobile 6.5. It features Sony's "tile" user interface and an 8.1mp camera. Other features include a 3.2", 800x480 screen, Qualcomm 528mhz processor, 1500mah battery, 256mb RAM, 512mb ROM, and is shipped with a 4GB MicroSD card.
From the advertisement's footnotes: "This device is 3G enabled for tri-band HSPA (850/1900/2100 MHz). Please check with your preferred carrier as some features, applications, and services are not available in all areas. GSM network with compatible radio band required. Not available in all countries. Local SIM card required to make local calls, sold separately. Check with a service provider for details."
So if you're on AT&T (or another compatible network) and are dying to get your hands on a Sony Windows Phone, now's your chance.