We go from the world’s thinnest laptop to one of the smallest smartphones with a full backlighted QWERTY keyboard, the Palm Centro.  The quad-band GSM Centro is only 2.1” w x 4.2” h x 0.7” d and weighs only 4.2 ounces with battery and is ideal for the business traveler.

It runs on Palm’s easy-to-use (if a little dated) Palm OS 5.4.9 and features a nicely-sized full-color 2.2” touch screen with 320 x 320 pixel resolution.

I found the five-way navigation button easy to use and the keypad made e-mail and texting a simple matter.  You can dial phone numbers from either the touch screen or the keypad – it’s good to have a choice since dialing with a combination QWERTY/phone keypad is always a bit tricky.  The Centro also supports push-to-talk service, useful for staying in immediate touch with colleagues and friends.

Nice touches abound, including built-in XM Radio, allowing you to take 25 of the best channels with you.  My online complaint: unlike the Sprint version, which supports 3G data, the GSM version only supports EDGE (Enhanced Data rates for Global Evolution) data services, which, while faster than GPRS at 100-130 Kbps, is still much slower than typical 3G speeds.

–David M. Goldes is a Contributing Editor of Executive Road Warrior and President and Senior Analyst at Basex, a knowledge economy research firm.