Previously I drove a 1985 BMW 323i which obviously performed slightly better, and was a little more nimble.
For approximately 6 months I owned a Kawasaki ZX-7R sport bike. It was so fast that it completely ruined my car driving experience. All of a sudden the BMW seemed so incredibly slow, that there was no thrill left in driving it at all! However, I didn't want to get killed on a sport bike, as I eventually would, along with everyone else who rides them. This lead me to purchase a safe, slow tank: The Mercedes 300d Turbo. It is fairly fast for a diesel car, but in the grand scheme of things it is a slug. This is fine with me, as everything else also seems slow after having ridden the sport bike.
Maybe I'm just getting old or something, but I find this big diesel tank with automatic transmission quite pleasant and relaxing to drive.
The engineering is good, from a quality standpoint.
I find that I use about 8 litres per 100 km, which is excellent mileage for a car of this size and weight.
Now that I've worked the bugs out of it, and corrected the problems which were due to the previous owner's neglect, I'm sure I could drive this car for 20 years with regular maintenance.
Parts are fairly easy to find, and priced resonably considering their excellent quality.
I only gave it a 6/10 for operating costs because in order to maintain the vehicle properly you do need to spend a bit of money, and there are no parts for $3 at your local Wal-Mart...so generally higher maintenance costs than a run of the mill domestic car. Heck, I could have bought a brand new domestic car for less money than this 15 year old machine, but this will probably still outlast one of those...
I would recommend it overall, but don't buy one that is priced lower than expected!!! You will end up spending more to repair problems than if you just bought a good one for a higher price to begin with. If you work on it yourself like me, then this might not be such a concern. Just be aware that a good deal will soon turn bad once problems start to surface...