I would watch out for the electrial hardware problem for the W210. My driver's side power seat failed twice when I had it in the first month of ownership. The dealer replaced the power seat motor and switch on the door. I don't have any problem since then.
Also, there are MANY complains about the fuel gauge not register at FULL. It does happen on my 99 E430 SOMETIMES. However, if you top the tank off with another 0.25 gallon, you MIGHT BE able to fool the fuel gauge.
Other than those problems, W210 is a very nice car to drive.
99 E430 Sport