Second, the camera has been upgraded to three megapixels in this release (though there's no flash or mirror). You can get pretty good results with this outdoors and in good light, but it doesn't compare to the camera you get on a Sony CyberShot phone like the K800i, and the lack of flash means its usefulness indoors is limited.
Third, and perhaps most importantly, HTC has also managed to squeeze in a GPS receiver, another significant addition and improvement over the original TyTN. This means you can choose from a multitude of navigation software packages – including the Wayfinder and Telmap systems I recently reviewed, or the more conventional CoPilot or TomTom Navigor software – and use the P4550 as your dedicated in-car sat-nav as well as your mobile office machine.
A more subtle difference – spotted by our ever-observant news editor Gordon – is that the P4550 opens from the 'other side' compared to the original TyTN. This means opening it with your right hand is easier, but if you like to hold your smartphone in your left, while jabbing it with your right, it makes it marginally less convenient to pop open.
Personally, I couldn't care less either way, and I think that most people won't give a fig either, especially when they realise that the screen, once extended to reveal the keyboard underneath, can also tilt upwards. When I discovered it could pull off this neat trick, a chuckling 'cool' escaped under my breath.
But seriously, the tilting screen is more than just a gimmick for geeks to drool over. It makes browsing websites and typing emails more comfortable because you don't have to tilt the phone at an unnatural angle to see the screen. And because the screen can be tilted to any angle between zero and 45 degrees it's far less prone to reflections than one that's horizontally fixed in place. It also means you can lay the P4550 on a table and jab away at the keyboard with your fingers rather than thumbs without having to crouch over the screen like a Tour de France racer hunched over the bars on a time trial bike. And, if you happen to have a Bluetooth keyboard you use for longer documents and emails, it means you don't have to prop the phone up in a cradle either.