My girlfriend has a 2004 SLK 200k automatic black/black. This is the newer model and looks better in my opinion (interior and exterior).
It's a very small car and the seats SUCK. I'm tall and my back hurts if I'm sitting too long in the seats. But the automatic hard top ROCKS, we drive it open everyday, today, yesterday - everyday when there's sun. Even if it's cold outside, it's still pretty warm inside the car with the top down if you turn up the heater.
We've never had any problems with the car (my gf put 10k km's on it in a year) but she has the newer model so I'm not sure how it compares to an earlier version.
The engine in the 200k is way too slow in my opinion by the way so I would definitely go for at least a 230k.
The automatic transmission is good (sometimes a bit slow if you floor it, it shifts down a gear or 2 automatically). So I had to get used to that. Overall, it's a cool, small car....especially in the summer and warm nights when you want to go to the beach etc. But I would think twice about it if you're over 1.95m. It just feels crammed if you drive it with a closed roof. It's no problem if you have the top down though.
