I have had troubles with the power sunroof, the covers on the inside got loose so I had to replace them.
In the beginning when I got the car I got it serviced at a Dutch Mercedes garage, but they are horrible, expensive and you have to wait much too long. Now I go to a German garage, they're much better.
Nice car, looks good, solidly built, too bad they were all a little cheap on the extra's back then in Europe, but overall a good car to drive.
Regarding the comments about the mechanics services, it's very important that you choose the RIGHT mechanics who should be dedicated servicing your 300TE as I also got a 1987 300TE and I extremely happy with my one which has done 212000 miles, but the mechanic I use has helped to make my one to continue to run well. If you use the wrong mechanic who are not so sure about Mercedes, they'll ruin your pride and joy!!So choose your mechanics carefully.