Hi All-
I simply hate Airmatic; leaking seals, level sensors, pressure sensors, air compressors, relays, fuses- something is bound to fail and usually does with our generation of Mercedes.
Here is the Arnott Coilover Conversation that I installed at home in my garage:

Arnott Coilover Conversion w219 w211

The website sells the kit for about $1700, but I found the exact same brand new kit on ebay for $1250 shipped.
Here is my review based on several factors including install difficulty, fit/finish/quality, and performance.

Install Difficulty. 7/10.
The front struts were not difficult.
Even working at a casual pace it took me only a couple hours.
There are lots of videos on youtube walking through every step.
The key is using the ball joint removal tool otherwise it is impossible.

The rear struts are really terrible.
There are a number of large suspension components that are really difficult to remove.
The Arnott installation video shows a methods that just doesn't work, and the issue is reassembling the suspension under pressure due to the springs.
It is certainly doable, and I am sure there must be some trick, but a crowbar and blood, sweat and lots of tears and time worked for me.

Fit, Finish, and Quality. 10/10.
Arnott is known for quality and reliability, and this kit is no exception.
All components fit perfectly and exactly matched OE specs.

Performance. 7/10.
Arnott struts make the stance of the car a bit higher.
I guess that is to preserve ride quality, which is very important to me.
However, the stance of the Airmatic Struts was much better.
You also cannot lower Arnott Coilvers, so this is not an options for those who want to "slam" the car.

The ride is a bit stiffer, which one would expect.
On the plus side, the suspension is much more responsive.
it just feels like more power is getting to the ground.
The car feels faster.
There is more vibration in the cabin but not a lot more, and the ride is still smooth overall, and there is not a lot of body roll.
I'm not sure if there is more or less body roll.
The increase height of about 1" is felt in the cabin going around turns, but the additional tightness for the coilovers reduces body roll.
Overall I think my car handles better around turns, but certainly not as good as with racing coilovers.

Overall Score. 9/10.
Aside from the ride height and lack of adjustment, there is not much to dislike about this kit.
IMHO the kit is best for people who want solid performance and acceptable ride quality, but most of want there car to work and not have F'ing random expensive failure.
Note the kit also comes with a bypass to delete the error message that I have yet to install.

Please feel free to comment!!