Palm continues to broaden its Windows Mobile lineup with the Treo Pro, an unlocked Windows Mobile 6.1 Professional smartphone aimed at corporate networks and at individuals who prefer the unlocked, unsubsidized route. In a first, Palm is releasing the Treo Pro only as an unlocked handset here in the U.S. (The Treo 680 and the Palm Centro have been available unlocked, but alongside carrier versions.) In testing the Treo Pro, it became clear that the company has learned from many of its prior design and interface mistakes with the 700w, the 700wx, and the 750 Treo smartphones.

Unlike Treos of old, the Pro measures a slim 4.5 by 2.4 by 0.5 inches and weighs only 4.7 ounces—surprisingly svelte considering that it packs so many features. In fact, it weighs 0.7 ounce less than the HP iPAQ 910, one of the Treo Pro's direct competitors and our current Editors' Choice for unlocked smartphones. The Treo Pro is constructed of glossy black plastic; combine that with its slippery, curved back and it ranks up there with the iPhone 3G as a serious fingerprint magnet.

The Treo Pro's QWERTY keyboard is more Centro than Treo, sporting the Centro's small, rubbery buttons. It's accurate, and it may be slightly wider than the Centro's, but it feels stiff and cramped overall compared with those of the Motorola Q9c, the HP iPAQ 910, or the BlackBerry 8800, all of which are significantly wider and more comfortable.

Still, plenty of thoughtful design touches abound. There's a side-ported speaker, so you can sit the phone on a conference room table and use the speakerphone without the usual muffled results. The hardware ringer and Wi-Fi switches are a joy to use, with the latter particularly handy in managing power consumption. There's a voice-mail notification beacon, built into the five-way control pad, that pulses every 5 seconds when you have a new message, so you don't have to power up the screen to check. The handset's screen-saver mode provides the date, time, and missed call and text message icons—another way to avoid using the screen's backlight unnecessarily.

The Treo Pro is an unlocked, tri-band 3G HSDPA 3.6 and quad-band 2G device, which gives it true worldwide roaming capability. In the U.S., it works on AT&T's 3G network and T-Mobile's 2G EDGE network. Its Wi-Fi radio connects to any 802.11b/g network with WPA or WPA2 encryption; it connected to my own 802.11g, WPA-encrypted network without a hitch. You can also tether the Treo Pro as a high-speed modem for your laptop. We connected the handset to a Windows Vista PC easily, and achieved speeds between 900-1500Kbps down and 270-350Kbps up on AT&T's HSDPA network.

On AT&T's 3G network, voices sounded loud, clear, and well-rounded. There was a just-noticeable hiss behind calls made in a quiet indoors environment, though, and the hiss wasn't eliminated when we reduced the handset's volume. But there's no in-ear feedback of your own voice in the earpiece. The speakerphone is loud enough for indoor use, but sounds too quiet in noisy outdoor environments. When the device was paired with an Aliph Jawbone Bluetooth headset, calls were clear and bright. Reception was a bit shakier than I was used to with other GSM handsets I've used in the same geographical area.

Built around a Qualcomm MSM7201 400-MHz processor, the Treo Pro has 256MB of ROM and 128MB of RAM, with 69MB free for user programs. In regular use, the phone felt a bit sluggish, lagging behind the average BlackBerry or Palm OS Treo. I suspect the sluggishness has something to do with the increased screen resolution; typically a 400-MHz CPU is powerful enough for Windows Mobile. For example, when dialing numbers, I experienced a delay before each key press registered; when I dialed quickly, you could hear audible distortion as the tone sounds piled up. Similar 2-second delays occurred when I switched between applications. On the plus side, I really liked the Task Manager that Palm has placed at the top right-hand corner of the home screen, with bright red "X" buttons that close application threads quickly.

Since the Treo Pro runs Windows Mobile 6.1 Professional, it hooks into Microsoft Exchange servers for direct push e-mail. It also works with up to eight POP, IMAP, or Web-based e-mail accounts. There's a full copy of Microsoft Office Mobile for creating and editing Word and Excel documents (or previewing PowerPoint files) on the go. For third-party software, Adobe Reader LE is preloaded, along with a slick communication manager for managing the handset's various radios, and a copy of Sprite Backup.—next: GPS, Camera, Productivity and More