I bought my TomTom One UK edition a couple of years ago, based on it's compact size, reasonable battery life (a couple of hours off the charge) and simple, easy to use software.

You can use the device right out of the box - just tap in the supplied Product code for your Map and you're away. However, you also get a software package called TomTom Home (for both Mac and PC, which is nice) that you can use to backup, update and customise your TomTom device.

The software also allows you to buy new maps, voices and other bits for your TomTom using it's own online store (this is basically just a link to a glorified webpage, but it works very well). Having recently bought a Western Europe map upgrade for my TomTom, I can testify that the download facility works very well - even over my less than reliable broadband connection.

The unit it'self works very well - it's reasonably fast to start up, and is very good at finding locking on to a good signal, even indoors or in built up areas.

The interface is very easy to use - you can typically do everything you need to do with just a few taps, although those with short nails or wider fingers might find themselves entering the wrong postcode occasionally.

Once you've set your destination, it generally only takes 5-10 seconds to calculate your route, however doing a recent home - Paris route took around 45 seconds, but then there are a lot of roads to think about there.

Sizewise, at under an inch thick the TomTom One really is small enough to fit into your pocket when you're not using it, so there's no reason to leave it in your car!

To use, the screen is easy to read, with both the main map and the upcoming directions situated so you only need glance at the unit to see what you need to know. Instructions are clear, and easily repeatable with a quick tap on the bottom left of the screen.

The only thing I don't like about the interface was that the battery gauge is not on the main screen, but rather on the Route Summary page - it's only one tap away, but I'd still have preferred some indication of battery life on the main screen.

I only really have 2 gripes with the device:

1. Postcode searches are only available for UK and the Netherlands, even on the Western Europe mapset - I have no idea why this is, it could just be something I've not downloaded, but it's not available 'out of the box' so it's a gripe.

2. The SD card you get with the UK version is not big enough to fit other maps on, so you need to go out and get a bigger card yourself if you download the maps. It's not a huge bugbear - a 2GB SD card can be had for around £20, but it's annoying that if you choose to have the map sent to you on an SD card from the TomTom website, it's the same price as downloading it.

Overall, there's not much to fault with the TomTom One - you don't get the battery life or extended map functionality of it's bigger brothers, but this is more than compensated by it's truly portable size and impressive price tag.