If, like me, you own an aging and increasingly bulky-looking Palm Treo but are reluctant to abandon the Palm OS, the Centro may be the interim smart phone you've been waiting for.

I say "interim" because the shipping unit I received today still lacks features that are routinely available on competing Windows Mobile and BlackBerry devices--most notably Wi-Fi and GPS support. But to get a Palm-like package equipped with those amenities, we'll probably have to wait for the Linux-based successor to the Palm OS, which isn't expected to appear before 2008.

And given what the Centro does deliver--Palm OS in its most contemporary and petite package yet, plus good mobile broadband support via Sprint's EvDO network--it's very attractively priced, at least for new users who sign up for a two-year Sprint contract and an all-you-can-eat data plan. The rebates associated with those contracts bring the device's nominal $400 price down to a palatable $100.

The Centro is significantly tinier (4.2 by 2.1 by 0.7 inches) and lighter (4.2 ounces) than its Treo kinfolk, and its smooth plastic case feels comfortable in the hand.

But it's definitely made of cheaper stuff than the Treo. I found the removable battery cover a bit fragile and somewhat difficult to remove and replace. As I struggled to snap it into place, I worried that the cover might break. Similarly, the skinny black plastic stylus feels as though it might snap in two if you looked at it cross-eyed.

I was confused by the small plastic door on the side labeled 'Micro SD': You can pull out the door with a fingernail, but the only way to insert the card is after you've first opened the battery cover. It would have made more sense if Palm had designed the door not to open at all unless the user removes the battery cover. As matters stand, the door is one more thing that might break if handled roughly.

Because the device is so small, its keyboard keys are proportionately diminutive, and I feared that typing would be an unpleasant experience. But Palm has done a good job here. The keys are coated in a squishy plastic that keeps your fingertips from slipping, and the keyboard's smaller size didn't slow me down much.

The transflective 2.4-inch 320-by-320 color touch screen looks good, though it's smallish. The navigation controls--an oval pad; buttons for the phone interface, the main Palm OS menu, the calendar, and e-mail; a red on/off button; and a green Send button--were responsive and easy to use.

To test the Centro's performance as a cell phone, I made several phone calls--with excellent results. The people at the other end sounded as good as on a landline, and they reported that I sounded great, too.

The phone supports Bluetooth, but I didn't have a chance to try it out with a Bluetooth headset (none was included in the package we received for testing).

Web browsing with the Blazer browser over Sprint's EvDO network was a sheer delight, especially since I'm used to the rather pokey speeds of AT&T Wireless's EDGE network on the Treo. Pages seemed to leap onto the screen, especially from sites that have been optimized for mobile browsers. Even nonoptimized sites appeared quickly.

E-mail setup went smoothly, but to use the Centro with my Windows Vista PC, I had to install new Palm desktop software that doesn't support e-mail sync over the USB sync cable.

One plus is that the Centro supports concurrent instant messaging sessions with the three supported IM services (AOL, MSN and Yahoo--a welcome development for anyone who has friends on more than one of these services.

Music and TV

The Centro comes with the Deluxe version of the PTunes music player, a nice addition. The preinstalled music sounded surprisingly robust through the device's rear speaker, but you have to be careful not to block the speaker by placing the phone on a desk with the display face up.

You also get Sprint's Music Manager software, which made transferring tunes easy. You'll need an expansion card if you want to play a lot of music, however, because the device comes with just 65MB of memory available to users--and you'll want to reserve some of that for applications.

The Centro's unmpressive 1.3-megapixel camera captures images at either at 1X or 2X digital zoom, and it can record a short amount of video. Image quality was adequate but nothing special, and Palm doesn't provide the image-editing tools that some phones with cameras now include.

I can't report back on Sprint TV: For some reason, when I tried to play trailers, the bundled Kinoma player stated that the format was not supported. Stay tuned.

The Centro comes with several other useful applications, including the excellent Palm client for Google Maps and DataViz's Documents to Go for at least basic editing of Microsoft Office applications. And I was a fan of the bundled Astraware Sudoku game before my Centro ever saw the light of day.

Sprint is offering two no-maximum data plans for the Centro. For $25 a month you can download unlimited e-mail and do unlimited Web browsing--but for unlimited text messaging (and IMs count as text messages) you have to purchase the $30-a-month plan. Though that isn't cheap, it's not out of line for 3G data services on a nationwide network.

When Palm came by the offices of PC World to show us a preproduction Centro last month, we were impressed by what we saw. The production unit largely lives up to that promise. It's not the most beautifully crafted cell phone available, but it's a good-looking contemporary handset looks--unlike the Treo, I'm sorry to say. And the low price certainly helps.

So while I'm waiting for a device that will support my legacy Palm apps and also provide the extras that I state-of-the-art devices on a competing platform offer, the Centro may turn out to be a satisfactory stopgap.

We'll update with a PC World rating once we perform battery tests. Again, stay tuned.