I got the new Nav6 yesterday and did my first ride on a sunny day today.
1) Direct comparison to Nav5
- the housing is absolutely identical in size (lenght x width). Except the screen is on the same level as the frame, and the whole device is therefore a bit thinner, but not much.
After a closer look, I noticed that the frame on the right side is about 2-3mm (0.1inch) smaller than on the Nav5 (i.e. the visible screen slightly bigger). As a result, the dashboard on the K1600 covers the visible screen on the right side a little bit. That was reported by other users as well, and it seems like there is no solution for this yet, except cutting off a small piece of the dashbard plastic (maybe BMW will offer a new dash, as they did when the Nav5 with the larger screen came out). It's not a big issue IMO, because it has no impact while riding, except that the button on the right side is partly hidden and therefore more difficult to reach with gloves.
After I backup'd all the files to my PC, I deleted the unnecessary files on the device (like foreign language files, help files, Basecamp executable, etc.). The device comes with 16GB memory, of which 14 GB are usable for data. After I cleaned it up, about 7Gb remain free. That should be enough for some time.
The "hidden" technical menu is still available and offers new options. One that sounds interesting is "Number of seconds before a waypoint is skipped". I will play around with this one and other new options as soon as I have the time.
2) First ride
This morning, it was sunny, so I took it for a ride. What a difference to the Nav5. While there are still some reflections in direct sunlight, it remains visible enough under all conditions, even in 3D mode. This was the main motivation for me to switch to the Nav6, and I don't regret it.
The other features (like "avoiding major roads", "circle tour", "tour in a given timeframe" etc.) are nice gimmicks, but not really relevant for me.
I wasn't able yet to test if it finally supports GPX 1.1 format. The Nav5 had issues with waypoints in this format. I will test this on the next longer tour.
Other than that, it acts like the Nav5, the menu structure is very similar (with all the pros and cons). The by far biggest difference is the screen and the visibility in sunlight.