My car is now 6 month old, covered 3200 miles, these are my thoughts.

The car looks great from outside, very muscular with AMG line which is the only option in UK. 22 inch wheels look good and no problem with air suspension which is standard on 450 in UK. Keyless entry works well but like others the key sometimes goes to sleep and has to be "wiggled" to lock or unlock car, not a big issue but should be sorted. Electric towbar is clever and still being able to open tailgate with gesture control is good. Selenite paintwork suits the car and is looks clean even when car is dirty, this is appreciated as I am not into cleaning my cars, I had the dealer treatment applied and I am glad I did. The intelligent lights are brilliant and I wouldn't be without them.
The engine is plenty powerful enough but I do miss the acceleration I had in my GLC43, only ..8 of a second but really makes a difference. Happy enough with fuel economy for such a big car, have averaged about 23 uk mpg which is about 19 us mpg. No issues at all with gearbox works well with the car.
Nappa leather standard in UK is really good and lots of seat adjustment, easy to get comfortable. Like the button on drivers door that allows you to adjust passenger seat from drivers side. Vast amount of room in 2nd row and in UK 7 seats are standard so 2nd row is electrically adjustable.Had a quick try of 3rd row but only for small people.Really like the fact that 2nd row can be raised and lowered electrically from boot. Only really notice that the 48volt battery is there when stop start cuts in, in previous cars I have always turned this off but no need to in 450 as it works seemlessly.. Mbux system is brilliant, lots of screens so you can find ones that suit you, touchpad is a waste of time, they should have left the wheel there and controls on steering wheel are fiddly. Touchscreen works well and resolution of screens is great.Not a clue why they have changed the easy entry/exit to include the backrest moving forward, I have turned seat movement off and just have steering wheel raising.
I have the off road pack, haven't used it for off road but have used it for going through water, it allows you to raise the car through 3 settings. Also not used the parking assistant, and limited use of the driving assistance but will use when I get more confidence in it.
Overall I am happy with the car and the only annoyance I have is that I don't believe the over the air updates are being carried out. As well as software updates it is supposed to do them for the Navigation in the area where you are located but I have had to carry this out manually 2 times in the 6 months.

 

I drove a service loaner GLE350 today and confirm the fiddly performance of Keyless Go. This happened twice in a 6 hour loaner experience. I also found the recessed door handle touchpads unnecessarily fussy.