Yesterday was genuinely the first time ever I have let Google navigate me fully all the way in rush hour, to be honest I was really impressed. Normally I make it recalculate when I have used it before as where it was taking me didn't seem logical.
It took me on roads I never knew and would have never used and I didn't sit in traffic once and that was from Gatwick to Sutton in Rush hour 8am with the M23 Southbound closed. I reckon it saved me 20-25 minutes! Looking online is it is both impressive and a bit scary, Google is drawing info and traffic speed from other peoples phones as long as they have location switched on and directing people like me around it. Is it really making these complex decisions live and real time just for me to get to A to B? Some of the moves would have saved a minute or so but I guess it all counts. Because I do not drive a lot I have never used it before as a 100% guidance tool normally only near the place I am going to if I do not know where I am going, but yesterday it was absolute chaos where I was starting out from and I had to get to an appointment. Sad as it sounds it saved the day I would have been very late, also I might not ignore the instructions in future again. I may also make sure my location is off, not sure I want to be part of Googles hive mind, although I enjoy the benefit! :-)
I would imagine the standalone Satnav are like the one built into my car, using roadside data and or FM radio. It is very slow at catching up with problems and it is not really live routing.