Of course all these advantages would be no good at all if they weren't put to good use. A sat-nav system must, first and foremost, deliver efficient routing, clear maps and timely voice instructions. And the 5100 certainly makes a good first impression.
I love the way it's so polite: you actually get a please before every voice instruction and, while other sat-nav voices grate, this one makes the whole driving experience that bit more pleasant. The 5100's map view is extremely configurable too: almost all screen furniture, including street names, ETA, speed cameras, time, altitude, speed and so on can be switched on or off to give you a very clean or cluttered look, depending on your preferences. To cap this, certain POIs pop up, complete with corporate logo - McDonald's restaurants with the golden arches, Texaco petrol stations with the red and white star logo.
There's automatic speed dependant volume adjustment, and by tapping the main map area it's easy to avoid a road block or traffic jam, set an extra interim destination or view POIs along your route.
On major roads and motorways the 5100 works very well indeed. Exits are indicated extremely clearly with big blue road sign-style banners across the top of the screen, major road numbers are read out by the device's speech engine and to add to this there's an innovative view of motorway junctions - called the 'reality view'. This displays the junction as a static graphic complete with arrows to indicate which lane you should be in. It's a good idea but I'm not convinced by this implementation: the few times it popped up while I was testing the 5100, it didn't really serve to clarify which lane I needed to be in at all.
As time wore on and the miles rolled by, I started to spot more serious weaknesses. What least impressed me was the frequently tardy delivery of the voice instructions. The system performs well out on fast motorways and A roads, but take it into a dense urban environment and it begins to struggle. Too often during test trips across central London, instructions were given at the last second, far too late for me to be able to respond in time if, for example, I happened to be in the wrong lane.