Here at the GoodGearGuide, we spend a lot of time fantasising about our ultimate GPS device. Curvy and sleek, this stylishly designed unit will possess the holy trinity of GPS design - ease of use, a large touchscreen display and pinpoint navigation accuracy.

When we first read about the GNS 8600 from Uniden, we thought perhaps our prayers had finally been answered. Here was a unit with just about everything we could want. However, as we were soon to discover, there are some significant flaws with this product which mean we'll have to keep dreaming for some time longer.

As you will quickly realise if you ever get to take a good look at one, the 8600 is huge. Bulky in the extreme and heavy to boot, the 8600 tips the scales at just under 500 grams. Without a shadow of a doubt, this is the biggest and heaviest GPS unit we have ever seen.

The reason the 8600 is so large is simple - the front of the device is dominated by an enormous 5.6" LCD touchscreen, allowing us to experience maps and driving directions in a level of detail we have never seen before. Practically, this meant no more squinting at the map in vain trying to read street names, having to reduce the detail of the display, or scrolling around madly trying to figure out just where we were, as the 5.6" screen displayed the Sensis Whereis maps in all their glory.

The problems with a device of this size soon became apparent when we actually took it for a test run. Realistically, the 8600 can only ever be used in a car. Don't even think about carrying it around because it will occupy a huge chunk of space in your bag - not mention adding half a kilo to what you're lugging round. Another headache we encountered is that while we didn't want to leave such an expensive piece of equipment in our car, we couldn't put it in the glove box because it simply wouldn't fit. In the end, we had to settle for sliding it under the back seat - perhaps not the most secure location for such a pricey piece of hardware.

Weight also counts against the 8600 when mounted in your car - since the unit is so heavy, the included vehicle mount can't fully support the weight and it tends to wobble and jerk from side to side when driving. To prevent this, Uniden recommend adjusting the mount so the 8600 rests on the dashboard. While this alleviated the problem somehwat, it did not eliminate it entirely and in the end we found the shaking highly irritating.

Despite the negatives associated with its size, some users may choose to overlook these and buy this product just for the large screen. However in our opinion, the major flaw of the 8600 is surely the fact that no internal battery is included. This means you can't plan a route when walking around, or in the house, or even in the car, unless it's plugged into a power source. We also experienced problems when using the 8600 in our car. When we got into our vehicle, we turned our ignition switch once (to the ACC position) without actually starting the engine, connected up the 8600 and happily planned out our route. Then, when we actually turned the engine on, the unit switched off and then back on again and we had to wait a few minutes for it to power up a acquire a location. While it did retain our programmed data, this delay was an unnecessary hassle and we feel an internal battery is a must have on a GPS.

Where this unit did score points was in features - as the 8600 is equipped with a multitude of navigation, safety and display options. We found the map display on the 8600 unit to be relatively clear, but not as bright as on other units we have tested and a little difficult to see in direct sunlight. Still, with such a big screen, the turn instructions were displayed clearly and the audio quality was excellent, so we never missed a turn. Voice prompts are generated before you take a turn and also at the turn itself, with the unit directing you to stay in the correct lane to ensure the turn can be made.

The map display itself can be viewed in 2D, 3D or displayed in day or night modes. Users can also toggle the map display if they like and adjust brightness, volume and calibration settings, as well as add their own Points of Interest (POIs) to the database of 500,000. Advanced routing options are also available, such as the using quickest or shortest route and including or excluding tolls, highways or other road types.

The 8600 ships with a range of safety features, such as a safety mode and warnings for red light cameras, speed cameras and accident blackpot areas. This warning was so accurate, we actually saw an accident take place just as the unit said "Blackspot Ahead"! A trip computer is available from the menu which displays both speed, time and distance data. Uniden has also included a 'route demonstration mode' as well, making this one of the most complete GPS units we have seen in terms of features.

We found navigation was simple on this unit as was searching for an address. While Uniden claim that the software for the 8600 was developed exclusively for them, it bears an uncanny resemblance to the software we've seen on the MIO units, such as the Digiwalker 268. It even comes with the same address searching functionality that relies on a predictive keyboard - one of the easiest we've used. As with the MIO 268 though, we were confronted with error messages in 'pidgin English' which really detracts from the professionalism of the interface.

Despite having such a large touchcreen, the menu, navigation and system option buttons are only displayed at certain times on the map display, and are not clearly labelled, so at times we weren't sure how to access certain functions. The 8600 also has four buttons and a four way navigation joystick under the screen, but again we were unsure what they did. We found out the Mode button actually lets you enter the GPS, play two games (a puzzle and Othello) and enter the system setup. The other buttons are shortcuts to often accessed functions but this isn't the most intuitive interface we have used.

Apart from useability, our second issue with the interface is speed. The 8600 is agonisingly slow. From the time it turns on, taking over a minute to fully start up, the 8600 tends to just hang or freeze for about 10 seconds, especially when calculating routes. Not only does this affect the interface, but also the rerouting, with unit taking precious seconds to realise we were off track and recalculate a new route. We don't mind a little lag now and then - but Uniden really need to upgrade the processor on this device to improve the performance*. Having said that, once up and running, we had no problem acquiring satellite signals quickly.

Unlike the majority of GPS units currently available, mapping data is not stored on a memory card, but rather on the internal 256MB memory. Map data can be updated by connecting the unit to your PC using the included USB 1.1 cable.

*Uniden have informed us that they now working to address slow processing issues on the GNS8600