Hi,
Just a quick observation. 3rd party GPS from my experience will all freeze when they loose the GPS signal which is sure to happen when you enter a tunnel. Try to get havelock road exit on CTE for example.
The difference I know having used the navi systems in my BMW's since 2002 is that for the in built BMW navi, when the gps signal stops the navi will read data from the car's speed and other telemetric details to estimate the position of the car so you never lose your position on the map and don't miss out on any underground tunnel turnings.
While you might still get away with it on CTE as there are still some breaks in the tunnel, once the KPE is fully built up, all of these external GPS solutions will show their true weakness and those with built in navi will realise why it was worth paying for a full fledged navigation system and not just a GPS toy.
Do remember where you heard this first....