My prior car was a 2002 Sports Coupe. At first, I missed the memory and Easy Entry/Exit features. But, as these were the areas where I had all my electronic glitches, they were missed less and less. All my friends appreciate the four doors.
The C300 is definitely quieter and smoother. Don't be fooled by the quiet, the acceleration is very good. You don't really realize how fast you are going. 1st gear in the manual is a bit low. But it picks up very nicely with the shift to second. While the engine is rated at 28 mpg highway, I have gotten over 29 mpg on long trips and over 31 mpg by using a lot of cruise control. This car without question feels more solid than its predecessor.
The quality of the leather is better, but the seats aren't quite as comfy as what you have now.
The Harmon Kardon sound system is a
vast improvement over the Bose option.
The command screen is fairly easy to use. It's the first time I have navigation in a car and it seems to work well.
Received my car in late March with no problems to report. Overall, I think most anyone would be pleased upgrading from a prior generation C Class.