Mine has never leaked. No fix was necessary. If mine did leak, it would bother me for sure.

I've had leaky seals on other cars, though. It's usually from dried out and cracked seals, assuming all adjustments are proper. If the seals are in good shape, a little silicone makes them seal better and may stop the leak.

There's isn't anything you can do about getting dripped on when you open the door... except wipe it up with a towel. But that's not a leaky seal problem.

The cars we're talking about shouldn't leak.

 

What Baz is talking about is a small pocket in the seal which holds ten or so drops of water and drips into the car if disturbed or will over flow during heavy rain while wind driven (that's a mouth full). Water seems to blow into this pocket and does not happen when you wash the car. My drip is the same thing. Very annoying. I'm not sure whether your SL600 has similar seals since we have the vario roof.

 

Beware of the leaks (plural). My wife's 1998 SLK230 leaks on the driver side. Also the rubber seal at the roof is leaking rain. Roof folding mechanism uses hydraulic pumps and they started leaking too.

Later SLK models' windows retract half an inch when opening the door, and closes after the door is shut resulting in better windows to rubber seal. I would buy later year models that has this feature. The problem with 1998 model is that when you adjust the windows tigher in upward position, the window does not closes well when closing the door (it jams on the outer part of the rubber seal). Because of this many of the newer cars have the roll-down-windows when opening/closing of the doors.

 

My wife's 1998 SLK230 had the following issues:
a. Headliner came off. $100 to redo it, not bad
b. Started leak rain through the rubber seal between windshield pillar and hard top roof.
c. Started leaking hydraulic fluid from the pump inside the hard top -- need to redo headliner when this is fixed. I understand that hard top retractor has several pumps and to replace all of the will run $2000.