and the common denominator is ?
Change. And not for the better. My old Garmin 2820 Brick was rock solid, easy to understand and use and never let me down till it couldn't cope with the over-bloated map data. Hell, it isn't as if Western Europe got bigger.
The old Zumo 660 was equally simple to use and again, never let me down until...see above.
The OEM nav in the old A6 was so intuitive and user-friendly (if somewhat clunky as it didn't have a touch screen) that I never needed to even glance at the user manual. It just worked. Of course, by the time the one in my A3 came along it had been 'improved' beyond all comprehension.
TomTom logic is not my logic and I have never been able to get on with it. And, as it turns out, nor is the new engine in the XT.
It looks and sort of feels like the old 660 at first. Then you start using it and wonder quite which motorcyclist was involved in the development of it. They have made the screen so busy that there is no room for a clock once you activate the mapping. So, it tells me when I will arrive at my destination but not how far in the future that is. I have to refer to the bike clock for that (good job my bike has a clock, not all do) and that requires me to look at yet another device.
If I want to type in a destination, some clever twit decided to break the QWERTY keyboard into two discrete screens, a left half and a right half with a button push to move between them. So, to type the word 'Scunthorpe' (not that that would be a destination of mine) you have to type 'Sc' then hit the screen shift key then type 'un' hit the key and type 't' hit and type 'ho' hit and type 'r' hit and type 'p' hit the bloody screen shift key and finally hit 'e'. Why?
Just a couple of examples. For others, see the plethora of moans on the net from mounts designed upside down so if it comes unlocked the device falls on the road as opposed to the old one which just wobbled a bit and stayed there to the inability to turn off the 'nanny state' bend warnings banners.
And the others who are moaning are not common to me.