We bought one of the coupes new in 04. My wife still loves it and plans on keeping it for 20 yrs. It's an auto of course, but being an 04 it got a new engine which is slightly smaller displacement, but same hp. With 72k miles we have had only small problems, both doors had to have the locking mech replaced because they had a problem with lack of lube causing the microswitch to go bonkers. Kind of expensive to replace, not a hard job but I didn't want to mess around with the air bags. Parts were only $125 but labor added up. Recently the thermostat started sticking so it triggered the check eng light. replaced that. On last service our good local Mercedes guy noted that the rear tranny mount had worn down enough to warrant replacing. Good support on the web, at MBorg and MBworld.
Car drives nice on the fwy, getting about 31mpg, driven cross country a couple of times. Lots of cargo room for trips to Lowes.
Lastly I had my first track day at road atlanta in it, was great, had sticky Conti sports on it. My instructor drove a bmw and was impressed at how well it did. I have also autox it a couple of times and it does fine, just use the manual mode and it will stay in 2nd for the whole run. Kind of fun breaking the rear end loose in a mercedes.
My mech says that the man gear boxes for mercedes are not real strong, so probably would keep that in mind.
In the end I would say I like the car, it's handy and sporty enough for a daily driver, when I get serious about getting sporty I jump in my supercharged miata. One time we drove her merceds and my miata back from Robeling Road to Pensacola and got exactly the same gas mileage,