Why spend more than a 150 quid on a sat-nav? It's a good question these days, when even the cheapest navigators have rechargeable batteries, reliable navigation and decent screens.

Mio attempts to answer it with the DigiWalker C620, a widescreen GPS that offers 3D elevation views, landmark graphics and high tech extras. It's available now for around £250.

Pros

Mio's build quality has come on in strides, and the C620 looks as good -- and is as easy to operate -- as any on the market. The 109mm (4.3-inch) touchscreen is bright, colourful and very responsive, showing its sharp 3D graphics to full effect. These consist of high resolution models of famous landmarks in key cities around the UK and western Europe, letting you spin around Trafalgar Square or potter up the Liffey to Trinity College.

The 3D view also makes use of new elevation data in Tele Atlas's impressively up-to-date maps -- the skyline show any hills on the horizon, and complex motorway junctions have roads ducking and soaring over one another. Speed camera data for the whole of Europe -- plus a year's subscription to updates -- is included.

Initial lock-on is a bit sluggish (allow five minutes) but the C620 holds its GPS signal well. Route calculation (and recalculation) is fast and accurate, and graphical directions are clear, with a useful auto-zoom function for turns. A one-touch side menu can also be summoned to give route data, turn-by-turn lists and GPS info.

Cons

Do you know how to 'prepare to enter a roundabout in half a mile'? If not, you'd better find out, as the Mio instructs to you do it with monotonous regularity. The C620 is forever barking orders at you, reminding you of each turn multiple times. What's worse is that the verbal commands -- available in a stern BBC male voice only -- omit road names and contextual information such as the direction of a roundabout exit.

While the hi-res 3D graphics are eye-popping, they're actually a step backwards for safety. The one thing you shouldn't do with any sat-nav is spend too much time looking at the screen, especially in busy cities. Having a gloriously realistic Arc de Triomphe sprouting from the Mio's centre certainly doesn't make navigating Paris's famous route any less hair-raising.

Linking to a Bluetooth phone for hands-free use is straightforward, although the Mio persistently crashed when trying to import the large contacts book from a Nokia 6110. Multimedia features (photo viewer and MP3 player) are basic and best avoided -- although you do get a SD card slot to add snaps with the USB link.

We never achieved the two hour battery life suggested by Mio, with the unit typically shutting down after around half that time.

Bottomline

Mio has devoted a lot of effort to the graphical side of the C620, but the minor advantage of 3D graphics isn't enough to compensate for annoyingly verbose and imprecise verbal commands. For less money, you can pick up the competent TomTom 720, which combines speech recognition with faultless mapping and ease of use.