I've had a black '97 C280 for just over a year, and I've really never been happy with the AC on days when temp is over 90F.
As I like to have the air distributed to both my face and feet, I realized last week that a good portion of the flow was going to the floor vents under the front seats. I plugged the vents with paper towels, and now it's really cold in the front with good flow to both face and feet.
Best part is that if you don't like the results, just pull out the paper towels.
Just come back in black E300 from Las Vegas vacations. Temperatures varied from 114F to 130 on parking lots, cooling down nicely to 95 about 4 AM.
I was really comfortable with automatic climate, although my wife would push the center vents other direction, complaining that it is freezing her elbow.