The name Treo has become synonymous with smartphone in the Palm world, going back to the original Treo 180 and then onto the Treo 270 and the Treo 300. While these devices worked well, they really only scratched the surface of what a PDA and cellphone combination device could do.

The Treo 600 is a vast improvement. The best Palm OS smartphone we've come across. While there are smaller smartphones in other platforms, such as Motorola, Samsung and Orange's Windows Smartphones, none offer the breadth of application support or the degree of integration that the Treo 600 does. The Treo 600's chief competition in the Palm OS world is the Samsung SPH-i500, a smaller device without a keyboard that leans more heavily towards the phone part of the PDA/Phone equation.

Treo 600 comes in two flavors, a CDMA edition for the Sprint network and a GSM/GPRS edition that is offered by AT&T, Cingular and T-Mobile. We took a look at the GSM version running on Cingular's network.

The Treo 600 has solid PDA specifications. It runs a modified version of Palm OS 5.2.1 which has been altered by Handspring (now a part of PalmOne) to work better in a phone environment. The Address Book, for instance, is noticeably geared more towards cellphone use, and in fact is a nice improvement over the standard Palm OS Address Book.

The Treo 600 uses a 144MHz ARM processor, not the fastest available for a Palm OS device, which tend to start around 200MHz at the mid to high-end range, but is still good enough to run most applications smoothly. One reason for a lower MHz CPU is to help increase battery life, a very important feature for a handset.

A powerful 1250 mAh Lithium Ion battery is integrated into the Treo 600. As a result, it gets much better battery life than the earlier Treos. The battery delivers 5 hours talk and 10 days of standby time worth of juice. Power-saving turns the device's screen off after several seconds of inactivity to help maximize power. Our only complaint about the battery is that it is not user-removable. This runs contrary to most handsets, which tend feature replaceable batteries.

In terms of memory, the unit includes 32MB of RAM (24MB available to the user), about standard for higer-end PDA, though there are a few like the Tungsten C (64MB), the TapWave Zoidac (128MB) and a some Sonys with more. The Treo 600 also has a Secure Digital slot, located on the top of the unit, that is SDIO enabled for both peripheral and memory expansion.

Treo 600, which measures 4.3 x 2.3 x 0.8 inches and weighs 5.8 ounces, fits very comfortably in the hand. It is noticeably thinner than the earlier Treo's. The flip cover design has also been replaced with a more user-friendly candy bar format. It also feels solid.

As a handset, the sound is clear and the volume adjustment, two buttons on the top right side of the unit, rests right next to your index finger for easy access. There is also a speakerphone option that worked well. We even conducted a meeting taking notes on a computer while on the Treo 600's speakerphone without any problems.

The Treo 600's thumb-keyboard is good as far as these things go. While we prefer the one integrated with the Tungsten C, as it is larger and you can capitalize letters simply by holding the letter down, the Treo's does offer backlighting, which is essential for a device that may often be used in dim lighting conditions. This is doubly important as the Treo's keypad is nicely integrated in the keyboard. There is also a virtual keyboard in the Treo's phone application that allows you to dial with a stylus or a finger directly on the device's display.

Above the keyboard, the Treo 600 has four application buttons and a five-way navigator button in the middle. One of the buttons accesses the phone functions, while the other hooks into the datebook application and a third runs a SMS application. The fourth button turns the device on and off and can be used to turn on the keyguard. The button and navigator combo of the Treo 600 greatly reduced the need with which we had to use a stylus.

The buttons can be re-mapped to other applications. We easily changed the SMS button to email, which we use much more often. Speaking of email, to get the POP3 email application up and running, simply enter your server, username and password info and you're all set.

With the 5-way navigator and the application buttons, Handspring did an excellent job of enabling users to perform many functions on the Treo 600 with one hand. This is an important achievement, as it makes the device feel and work more like a handset.

On the back of the Treo is an integrated digital camera. Pictures taken with the 640x480 resolution camera won't win any awards but it certainly is convenient. It is easy to take a picture and send it out in an email message or use a photo you've taken to ID a caller. The smarpthone's display serves as the viewfinder for the camera.

The smartphone's 1.8-inch display is small for a PDA but large for a handset. It is quite bright indoors and works well outdoors. Unfortunately, the screen's resolution is only 160x160, which suffers in comparison to the high-resolution displays found in most other high-end Palm OS devices. If you've become used to the 320x320 or 320x480 resolution of some Sony and PalmOne handhelds you'll be disappointed in the Treo 600's screen. The screen is also only 12-bit, which means it can display 4,000 colors compared to 16-bit or 65,536 color displays. Nevertheless, a new user won't notice the difference until they see one of these other device's in person.

The unit features Blazer browser version 3.0, which has been completely rewritten from earlier editions yet maintains a similar user interface. Unlike the earlier versions, this one does not use a proxy server, meaning it pulls web pages directly from sites rather than processing and formatting them first through a server for handheld consumption.

Since the Treo has a small screen, the browser, like in most PDAs, still needs to reformat the pages. It does this by turning a page into a single column. Browsers that don't do this require that you scroll from side to side to view information which is inconvenient. We were able to download most web pages. Even though GPRS, the data part of GSM network, is fast, you'll still need to wait a minute or two or even more for most complex pages to load.

So the Treo 600 delivers a lot and is a giant step in the right direction for a Palm OS smartphone. It has a good amount of memory and battery life, a usable digital camera and a well integrated keyboard. It is an admirable PDA. But more importantly, its PDA functions doesn't overwhelm its usability as handset. This balance, between PDA and handset, is what sets the Treo 600 apart from other smartphone solutions.

As a side note, recently, rumors have circulated about the next device in the Treo 600 series, the Treo 610. It seems that the next Treo will be very similar to the current version, but with a high-resolution 320x320 pixel display, just like most of its PalmOne brethren. In addition, expect the next Treo to also integrate Bluetooth to allow owners to use Bluetooth-enabled headsets. While this would be the chief benefit of Bluetooth, eliminating wires, users would also be able to connect to other Bluetooth-enabled devices such as printers. The new Treo is also rumored to have more memory. The rumors place the debut of the new Treo to be March, but nothing concrete is known. And just because a device may be announced doesn't mean it will be available at that time. It could till take another few months for a carrier to add it to their product lineup.