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.