Boasting an "arc-slider" design, a QWERTY keypad, and an innovative paneled interface, Sony Ericsson's first stab at a Windows Mobile smartphone looks like a winner, give or take a few rough edges. Check out my hands-on impressions from Vegas.

The Xperia X1 was a big hit at last month's World Mobile Congress event in Barcelona, but apparently it spent its moment in the spotlight stuck in a glass case. This week, Sony Ericsson reps were finally ready to air out the X1 during CTIA, and I got a chance to give the sleek handset the once-over.

First impressions: The phone itself is beautifully constructed, what with its black, brushed-metal back panel and silver keypad, and the handset slides open with a solid, spring-y action. The Xperia's "arc" design leaves the display at the perfect angle while you're typing.

That said, the Xperia is not a small phone. The handset weighs well over five ounces, and at 4.3 by 2.1 by 0.65 inches, it's no svelte iPhone (although, to be fair, it's not a monster like the Nokia E90).

Also, about the metal QWERTY keypad: It's gorgeous, all right, but during my brief testing, the keys felt a bit small and slippery to my fingertips. It could be something that you'd get used to over time, but it's worth noting.

Back on the plus side, the wide, three-inch WVGA display looks great, and the phone itself runs the professional version of Windows Mobile (yes, it'll be the newly announced version 6.1), complete with a stylus. There's also a four-way navigational keypad and an "optical" joystick—a little nub that you swipe up, down and across for scrolling through menus and Web pages.

One of the most intriguing features about the Xperia are the nine "panels" that sit on the phone's main screen. The panels can be just about anything—Web pages, widgets, applications—and tapping one of them brings it to the fore.

One panel that the Sony Ericsson folks were particularly proud of looked like a blank desktop save for a few colored fish and a digital clock. Tap and hold the screen and the fish flock to your finger; tap repeatedly and the fish scatter. If your battery's getting low, one of the fish starts to turn red, while another fish turns yellow if you miss a call. Cool.

My Sony Ericsson rep said that the company's looking to developers to build even more panels, which can be displayed nine at a time or splayed out like a deck of cards.

Running beneath the panels is, of course, the pro version of Windows Mobile, which boasts your standard lineup of mobile Office, PIM and media apps. Unfortunately, the OS was running excruciatingly slow on the Xperia I saw; the reps assured me that the Xperia software will be tight as a drum by the time it ships. Let's hope so.

The Xperia doesn't disappoint when it comes to connectivity—full-on HSDPA access (yes, even here in the States), Wi-Fi, and Bluetooth. Also on board is a 3.2MP camera with touch auto-focus (just touch the viewfinder to pick a focal point—nice!) and AGPS navigation.

So, when's the Xperia going to arrive? I'm told it'll be here in the second half of the year, quite possibly with a carrier (AT&T is my guess, although Sony Ericsson would only say that talks are "underway" with carriers unnamed). No details on pricing either, but from what I've seen…we could be talking upwards of $350 or more, even with carrier subsidies. Stay tuned.