We have owned our ML55 for over 3 years. Lots of plastic replacement. Idiot lights come on when driving; turn engine off and back on and they disappear. It's very hard to keep aligned. Great engine and tranny! Rides like a Wrangler with stock KYB shocks. It was a rush job to market to be sure but with some tweaking can be a lot more fun to drive and less costly to maintain then stock.
Engine power is smooth. Incredibly smooth and quiet. The 5 speed automatic is dreamy!
Get rid of the plastic and add real wood. Improve the ride by getting rid of the KYB's in favor of Bilstein shocks. Get rid of the soft brakes and rotors.