Read Marc Noordeloos's comments on driving the 2008 Mercedes-Benz C300 4MATIC.
The C-class is a real pleasure to drive after the Cadillac CTS. It is smooth, relaxing, and it has a nice open feeling inside. The suspension is well tuned and the steering has good weight and accuracy at low-speeds (I didn't go above 50 mph so I can't agree or disagree with Sam's notes). I love how the C-Class feels like a real Benz going down the road. I still think the interior is quite low rent compared to other cars in the class. The plastics on the dash and steering wheel aren't fantastic and the climate control knobs lack a quality, tactile feel.
To answer Sam's question, you can't turn ESP all the way off on non-AMG Mercedes models. And, yes, the system does do some weird things in the "off" mode.
I also found the car had good forward traction in the snow but braking and handling highlighted that all-season tires can only do so much.
I didn't have any issue with headroom, surprising given my hair. I also don't mind the sat nav screen but I see Sam's point. At least the map screen is very clear and full of info.