Never heard of problems with ABS and traction.
They are very reliable cars. I have a 88 300CE and I just sold my 90 300E. My CE has 125k miles, I never had any problems with the car.
However, I've done many AC jobs on other 124s. Most evaporator jobs on Mercedes models involve taking out the dash, a lot of labor involved $$$. Have the system checked by a professional. I did an evaporator job for someone that owned the car for less than a week. I guess the previous owner just added some freon before sale.
Another thing to look out for is head jobs: gasket, seals, guides, chain etc. Make sure that the car had some work on it done or else deduct from price.
Check for engine oil leaks and transmission seal leak. Check transmission fluid quality. Smell the fluid after a test drive.
Just make sure the car was maintained properly. A lot of times you can tell by the seller.
Another thing to check are the instrument panel fault lights. Make sure they all turn on when key is in ignition position. A lot of times people disconnect the bulbs.
[Edited by vinamg on 01-18-2001 at 12:13 AM]