Here are my results. Though I used the Climate Control to get the temperature; I didn't put a thermometer in the center vent. It might be a little colder assuming the sensor is down in there.
With climate control on AUTO and LOW... when driving (roughly 30 mph), on low fan speed, the temp is between 35 and 42 F. When it's the fan is on high speed while driving, it is about 41-46 F.
Alright, now when I'm stopped, with the fan on high speed, the temp is between 48 and 54. While stopped with the fan speed on low, the temp is between 41 and 48 F.
Seems fairly normal to me I guess. But this is using the onboard temp sensor.
2006 E350 w/ 155k miles (Daily Driver)
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)