My last vehicle was a 2008 ML 320 CDi and I loved it. The diesel is fantastic, tons of low end power, incredible economy for a big heavy vehicle and really a great sense of overall quality. I never had a single problem with it. Amazing for towing, my 5,000 lb boat and trailer was easy to pull and safely under the 7,200 limit.
The Artico seats are fine. That stuff showed zero signs of wear after a couple of years and those seats were are so comfortable.
The only reason I got rid of it was my commute dropped to 25 km round trip per day and we had a paid for 2010 minivan in the driveway. I miss it though. Don't miss the lease payment or expensive routine maintenance either!
Enjoy!