Sony Ericsson's Xperia X1 Takes the Windows Mobile Plunge at the Mobile World Congress.

Barcelona this week was the world showcase for new mobile phones. Due in this year, the Xperia X1 goes where Sony Ericsson has never gone before--into the realm of Windows Mobile. But thanks to a custom interface featuring nine square panels--each of which launches a different application--you might not realize that you're looking at an HSDPA handset based on the Microsoft platform for mobile devices. The X1 is the first entry in Sony Ericsson's new "premium" (read, expensive) Xperia line; future models may be based on other operating systems. But observers say the company chose to stray from its Symbian/UIQ roots to reach out to corporate customers.

Xperia X1's large (3-inch) touchscreen exemplifies another handset trend. But it also lets you navigate via an optical joystick underneath the display. When closed, this Sony Ericsson's metal-finish rear case shows nothing but the lens of its 3.2-megapixel camera. However the X1 does have an unusual design feature: It slides open sideways in a gentle arc to reveal a roomy portrait-mode keyboard. As with other sideways sliders, the display adjusts automatically.

The G700--Another Touching Experience from Sony Ericsson

The G700, another eye-catching touchscreen phone announced by Sony Ericsson, sports an unusual sticky-notes application. Tap the note icon in the upper left, and a new blank note fills the screen. You choose the note's color and screen position, and use the phone's stylus to scribble or draw memos. Sony executives compared this handset to the Post-It-covered Filofaxes of a decade or two ago.

Sony Ericsson's Two Cyber-shot Phones Step Up

The higher-end of two new Cyber-shot phones announced at the Barcelona gathering, the C902 boasts a five-megapixel camera accessed via a new slide-apart design that's touted as able to capture images "within an instant." Other advanced technology includes auto-focus, face detection, flash, and image and video stabilization. The C702 has a 3.5-megapixel camera and geo-tagging features using assisted (by cell technology) GPS, a.k.a. aGPS.

Walkman 980A--A Clamshell You Don't Have to Flip Open

Sony Ericsson's newest Walkman phone is designed to appeal to clamshell aficionados who might not want to see a keypad just to play music: The entire Walkman player interface appears on the exterior. The handset has 8GB of internal memory (same as the current smaller-capacity iPhone), and an FM transmitter to beam music to your car or home stereo receiver.

Samsung Adds Soul to Its Lineup

You can't go anywhere at the Mobile World Congress without seeing huge banners touting Samsung's Soul, the undisputed star of the company's lineup. Checking in at an eyelash over half an inch thick, this super-slim metallic HSDPA (the fast 7.2-megabit-per-second variant) slider phone has a 2.2-inch display with simple icons showing its applications--controls on the a haptics-enhanced OLED navigation touchpad below the display change depending on application. The Soul also packs a 5-megapixel camera with face detection and image stabilization technology, as well as Bang & Olufsen IcePower amplification for music playback.

Samsung's G810: A HSDPA-GPS-Wi-Fi Camera Phone

At seven-tenths of an inch thick, it may look positively chubby next to the Soul, but the Symbian-based G810 does offer a few things the Soul doesn't--most notably Wi-Fi (for when its 3.6-mbps HSDPA isn't fast enough and you're near a hotspot) and assisted (by cell technology) GPS with geo-tagging support. Other goodies in this Symbian handset include a 5-megapixel camera, a 2.6-inch screen, and TV-out port. Another one for the European market only, alas.

Samsung's SGH-400: Speakers at One End, Keypad at the Other

The SGH-400 music phone with its dual slider design. Slide the back up to see some serious-looking features; slide it down for the usual keypad. It too has Bang & Olufsen IcePower audio technology and a 3-megapixel camera (which is almost chintzy in this year's crop).