I just completed the cyl head gasket change on the E320 this past Sat morning and during the initial run it ran a little hotter than normal (got up to around 105 dC). This was with a fill of radiator flush and straight water. I ended up flushing the system with straight water three times. Fill with straight water, run the car to temp, let it cool, drain radiator and block and refill. The manual does say that the head gasket does not seal until it has been run to temp. Don't forget to turn the heater up wide open to insure water flow through it too.
Finally, I made up a mixture of one bottle of water wetter, approximately 40% MB coolant and the remainder distilled water. Made a trip to Atl on Sunday and it now runs between 85 and 95 dC (based on whether sitting in traffic or on the interstate). I do have a very, very slight miss when it is at operating temperature at idle and I am working through that issue but otherwise the car runs great and I am getting the gas milage I am supposed to be getting. Unless you were really "feeling" for the miss you would not even notice it.
Go to your local parts house and get a coolant mixture tester. It is way easy to have too much coolant in the mixture which will make it run at elevated temperatures.