The latest edition of HTC's Touch smartphone line is now available in the U.S. Unlike the original all-touch-screen Touch models, the Touch Dual sports a 20-key keyboard that slides out from underneath the display. The idea is to make it easier to input text for working on documents as well as sending SMS and e-mail messages.

Of course, being a HTC Touch and all, the Touch Dual features HTC's proprietary TouchFLO interface, which runs on top of Windows Mobile and allows for finger-touch scrolling, panning and photo zooming, for example.

The Touch Dual, a quad-band GSM world phone with support for 3.5G data transfers, isn't available directly from any carriers. Rather, HTC is selling it unlocked through Best Buy and its own retail site for $550.

This means if you're a customer of a GSM carrier like AT&T (the only American operator with support for GSM-style 3G and 3.5G) and T-Mobile, which finally just began rolling out its 3G service (in the NYC area), all you'll need to do to use the Touch Dual is pop in your SIM card.

Additional features include a 2 megapixel camera for photos and videos and a second camera for video calling. It's got 128MB of RAM, a microSD slot for storage expansion, and a 400MHz processor.

There's no Wi-Fi, though, which may not be that big of an issue with 3.5G support.

It weighs 4.2 ounces and measures 4.2 x 2.2 x 0.6 inches.

Significantly, the Touch Dual will be one of the first devices run Microsoft's just announced upgrade to Windows Mobile upgrade, version 6.1, which provides new timesaving features, easier phone navigation and management, stronger security safeguards, and support for Microsoft System Center Mobile Device Manager 2008.

HTC, normally a behind-the-scenes player that builds smartphones from others, has spent the last couple of years slowly stepping out of the shadows. It recently launched a major marketing and advertising campaign to speed up the brand-recognition process in North American, though.

In addition to print and online, the HTC advertising campaign includes outdoor (subways stations, airports, etc.) and TV (cable, in-flight and movie theater placements) advertising.

Head over to HTC's new YouTube channel to check out its first television ads.

By now, HTC's sold well over 3 million units of its Touch line of Windows Mobile-run smartphones.

Last month, Verizon became the latest American operator to deliver the original HTC Touch model, as the XV6900.

Earlier this week, HTC debuted its next-generation Touch model, the HTC Touch Diamond, with a new, enhanced, 3D edition of the company's touch screen interface and a number of other improvements.