If you've been weighing up your Smart phone options you'll have realised that there are many sub-species. Broadly these fall into three camps: phones with some capability to manage your diary and run third-party software; PDAs that have telephony features built-in; and true hybrids that look like neither a phone nor a PDA, which integrate both types of functionality.

The new Treo 650 is in the third camp, and if your needs are relatively humble in the crash-bang-wallop multimedia department, but you want a good mobile Internet device you can use at home and at work, then it is definitely worth considering.

The Treo 650 updates the Treo 600 that has been in the Orange Signature Phone range for some considerable time. Orange was represented at the Treo 650's UK launch at the end of April, so you could well expect the Treo 650 to become a Signature Phone too in the not too distant future.

The basics that made the Treo 600 great have not changed, and where they have it is for the better. It's a shame that PalmOne has not gone a little further than it has with the Treo 650 though. Let us explain...

This new device is more usable than its predecessor, with its QWERTY keyboard sporting larger keys and a new, better arrangement of shortcut buttons. PalmOne retains the button on the top of the casing that shifts the phone into silent mode. Profiles suddenly seem a completely unnecessary idea with this option at your fingertips.

The screen is now 320 x 320 pixels, and these are crammed into a space 2.5 diagonal inches in size, making the screen image clear and sharp. And the integrated communications features have had a boost. Apart from some nice software tweaks to the dialer screen, you get VersaMail, PalmOne's own e-mail software, which can collect POP3 mail at scheduled intervals.

Better still, you can set two time frames, getting it to collect frequently during working hours, infrequently at other times. You also get Blazer, PalmOne's Web browser, which is good at formatting pages for the screen size, and allows you to download pages to read offline, which is handy. Documents to Go is provided on CD, allowing you to read Word, Excel and PowerPoint attachments and create native Word and Excel documents.

RealPlayer is pre-installed for music, and there is a built-in camera. Here we hit some issues. The camera is not state of the art - its maximum stills resolution is only 640 x 480, and RealPlayer only plays music from SD cards, though frankly with just 21MB of user memory available you are going to need a card or two anyway. The only good thing about the memory is that it will survive if the Treo 650's battery fails.

Bluetooth is included and our own Bluetooth headset paired first time and worked fine thereafter. The battery is removable, which is always a boon, and we managed to get away with charging every couple of days during testing, though we didn't play much music, being disgruntled at having to carry a converter for the 2.5mm headphones jack.

Pricing is not confirmed as we write this review, so we can't take that into account when pondering the verdict. But we've been fans of the Treo 600 for a while, and the 650 plugs a few important holes like adding Bluetooth and improving the screen resolution. It's a real pity about the lack of onboard memory, though.