The main reason I bought Sat Nav was for alternate routes.
In Dorset where the centre road markings are mostly still grass there is one main road across the county.
Nowadays one only has to break a toenail and with health and saftey guidelines, the police or council will close the road. Eventually they may put in a few diversion signs, later they may even join them up.
The only alternatives are the long diversions or taking a chance on winding side/country roads where it is very easy to take a wrong turn and end up back at the same queue or going in completely the wrong direction, hence the decision to try Sat Nav. A recent local road closure highlighted that the official diversion to travel the required 100 yards was in the region of 16 miles as they have to use main routes where possible. Local route was about 1.5 - 2 miles. Things will only get worse in the Weymouth area as part of our road improvements process involves closing the alternative routes completely.
The Dorset roads are often so narrow there is no place to stop and look at a map, but if this is the main reason for purchase then as a review, I am not sure if the TurboDog package on the Navigo is the best solution as I have great difficulty in using the map exploration features!
Re Speed Cameras: not wanting to start a debate, it is obvious from the GPS data that the speedometer reads low on my vehicle, now in our area if the police don't like you they will prosecute you for doing 34 in a 30 limit, nothing to do with safety as they themselves beetle about at far greater speeds on their way to tea. However they mostly have the same speedometers as us!
So the GPS logging information is useful, as is a reminder that one is approaching an accident blackspot area.
One chap programmed a logger into his GPS phone and when prosecuted for speeding, stated that he was not guilty, their speed camera(laser) was obviously faulty and he would be producing the GPS logging evidence in court to prove his claim. Surprisingly the case was quietly dropped.
Back to the subject:
Decide what you want from the system and check all the reviews that you can find to decide on the best one. A cheap system is not cheap if it doesn't do what you want, on the other hand by well defining your criteria, you may find a slightly more expensive cheap solution that matches perfectly.
I quite like the idea of being able to take a picture on the trip with the SAT Nav and then later reviewing it and finding out where it actually was as opposed to "somewhere we drove past that day", although I do not think the current price tags for such systems, particularly as I am not doing much driving, justify it enough for me.