I heard this on the radio this morning so I googled it. Even for 2007 Mercedes M Class was Worst in Reliability for Mid size SUV. Consumers Report.

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Midsized SUV
Best: Toyota Highlander Hybrid (slighly better than the regular Highlander)
Worst: Mercedes-Benz M-Class
I still enjoy driving my Mercedes. Its my 1st Mercedes and probably my last.

__________________
Steve Danville
what i did myself.
CPS
rear shocks
MAS x 3.
SparkPlugs (twice)
Fuel pump & Filter
Window switch
replaced both failed horns with Honda horns.
Cleaned ERG Tube
Oil changes
Oil consumption Fix
Brake Pads
A/C Recharge
Anti-Freeze change X 2.
Front Shocks. Monroe. $90
Mercedes Warrenty Work:
Harmonic balancer,power steering clamp. Cat converters.Drive Shaft Bearing.s
Replaced Outer Lower Tie Rods and front lower ball joints at 156,000 miles