I personally think that Canon fell over their own feet when they came out with the 6D Mark ii. However, I have had my copy for about a month now and certainly don't consider it a bad camera. In fact, I am really beginning to like it.
Let's get a few things out of the way...
The original Canon suggested retail price of about $2K USD is way higher than the camera should sell for. I got mine for about $1.3K USD (after rebate) along with a Canon OEM battery grip which I have found that I really like - Another neat thing about the battery grip is the ability to use a hand strap (as was pointed out by Donald). I used a hand strap on my 7D connected to a RRS L plate, two extra (third party) batteries + charger along with the Canon Pixma Pro 100 printer and 50 sheets of 11 x 13 inch Canon paper was included. Canon also threw in a year of accident insurance.
There is no 4K Video. Well, I don't often shoot video with my DSLR. However, with the articulating LCD and great live view AF, I might just start using the 6D2 for my dog videos for which I don't need 4K. I am also looking forward to playing with the 4K time lapse feature (see this YouTube video: https://www.youtube.com/watch?v=-2FKlfUyAQ8).
The elephant in the room is the dynamic range which is lower than the previous 6D as well as many other cameras. This is a factor I must live with, although at somewhat higher ISO levels, the difference is not as great as it is when shooting at ISO 100. In fact, I am pretty happy with the general characteristics of this camera at say between ISO 320 and ISO 3,200.
There is only one memory card slot. I no longer shoot professionally and even though my 7D2 has two slots, I normally shoot with just the CF Card. However, I wish that the one slot in my 6D2 was a CF, not SD. I like CF cards better and I own a good selection of top brand CF cards.
There are some things that I really like about the 6D2! Surprisingly, the articulating touch screen LCD leads the features I like (I really never thought that I would like that!). The dual CMOS sensor allowing good live view AF also helps. Additionally, I like either using the touch screen for focusing or for focus and shooting and for menu selection. It does a very nice job with pulling focus in video and it is great for focus bracketing. It is also is nice for night focusing (I use a stylus) of cityscapes...
I like the AF - which is better than my full-frame 5d2 but, not quite up to my 7D2 (because the focus points are bunched towards the center). The 6D2 allows me to use my 100-400mm f/4.5-5.6L IS ii lens and still retain AF with a 1.4x sensor as does the 7D2 but, not the 5D2. The AF is fast and accurate on the 6D2...
I like the excellent battery life (especially with the grip attached) and can also use the batteries from my 7D2 interchangeably.
I like the 7 shot AEB bracketing.
The camera and battery grip fit my hand quite well.
The learning curve between the 6D2 and my other Canon DSLR cameras is not that great at all and, of course I can use all my Canon EF lenses with the 6D2.
I really like the ISO 1,600 results... That gives 6D2 makes a really nice low light capability with the Canon EF 35mm f/2 IS lens.
There are other interesting features but, I am still in a quandry whether I would recommend this camera, especially for a one camera owner. I do like it better than my 5D2 and it was a bit less expensive than a used 5D3. I like shooting with a full frame camera for dog photography since I don't have enough room for full body shots of larger dogs in the area that I shoot (using my favorite dog lens, the 70-200mm f/4L IS). Additionally, a full frame camera with my 70-200mm f/4L IS lens combined with my 7D2 and 100-400 Mk2 is a great combination for shooting people outside.