Sony may not be a name that springs to mind when thinking of satellite navigation, but the company's heritage as a TV manufacturer and its design ethos shine through in this device.

The Nav-U NV-U51G is one of the prettier looking GPS units we have seen. And like previous Nav-U devices, it has a good quality 3.5in screen, making it easy to see in the car, and it gives clear, audible instructions when used while driving. Unfortunately, that's about it for its highlights.

That's not to say it makes no improvements over previous versions. You can now, for instance, search by full post code, making it easier to pinpoint the exact location of a destination. But yet again, Sony has failed to provide a memory card slot, limiting the opportunity for expansion. It comes with maps for the UK and Ireland, and it is possible to buy additional maps, adding them to the unit using a PC.

In use, we had mixed experiences. The Nav-U uses Navteq maps that were up-to-date (we tested it on some recently completed roads), but we found that at times it was slow to get a GPS signal. And annoyingly it occasionally dropped the signal while we were driving.

We've used more intuitive sat navs too, although we got used to it after several journeys. The device uses gestures on its touch screen (for instance, drawing a line with a finger rather than pressing a button) for some functions, which took some getting used to. It's a feature users will either love or loathe.

The device's ability to re-route when the driver takes a detour depends on the route profile he or she has set up. Tell it to pick the fastest route and it is slow to change, instead persistently insisting you perform a U-turn. But set it on 'optimum' or 'nice' (Sony-speak for scenic) route and re-routing was pretty much instantaneous.

After a few trips we realised that if we planned to alter directions mid-journey, it was best to pick the latter journey options and ignore the 'fast' mode.

It was able to give us enough good journeys where it guided us effortlessly to our destination, but before buying we’d suggest looking at alternatives in its price bracket.

Vista compatible: N/A