Like most of us, I suspect, I too have labored under this issue of "Is my engine running too hot?" I wish I could really remember what mine was like when I first got it (3 years old, 25 k mi on the clock) but I was not as finnicky or observant then as I am now. The preponderance of the data I've read lately is that just about anything under 110 is OK. Even then, I am not reassured. This winter, it's been mild here, so we have been getting lots of 40 degree F days. On those days, on the interstate, my temp is around 85-90. Seems to me that it SHOULD be 80, like it is when the ambient temp is 35 or below. But then I read that 87 degrees on the coolant gauge is perfectly normal, and that running cooler puts more wear on the engine.
Part of the "problem", if there is one, is that MB uses a linear gauge. Most other manufacturers fudge on gauge readings, probably to prevent owners from complaining and running up needless warranty claims. Every Ford and Toyota and Honda I've owned has had a rock-steady temperature indication once the engine is at operating temperature, every day of the year. THis is an artifact of the electronics used, since I'm pretty sure just about any engine should show some variability in temp depending on season, stop-and-go vs. 75 mph, etc.
MB engineers apparently think we "CAN handle the truth" to paraphrase Jack Nicholson.