I have a '98 and really like it. It's really not that bad to work on and I have done practically all the work on it since I bought it. I was reluctant at first to work on it but after seeing what "pros" do I decided to do it myself. I bought mine with 115K on it in January '05 and have put 20K on it since then. It runs better now than it did when I first got it. Mileage is up to 30 MPG average with 34 on the highway and it uses virtually no oil between changes - for a car with 135K miles on it that is quite a feat.
But I did have some issues since buying it...none major, just annoying. MAF sensor ($135), turbo wastegate solenoid ($115), auxilliary fan ($175) and starter relay ($25) are all electronic glitches and are common. It also developed a very small leak at the thermostat housing so I replaced that along with the T-stat ($60). None of these issues was "life threatenting".
When I bought it I had all the glow plugs changed, all the fuel lines and filters changed and transmission serviced - that was before I did work myself and I would not hesitate to do any of those jobs now.
Now I just change the oil and filter and drive. Based upon what I paid for it in '05 and all I have spent on it I could probably sell it today and have driven it all that time and not lost a cent...that's worth something.
I guess my advice would be not to buy one unless you can do work on your own...if you pay a tech to fix those little annoying items each one can be equal to a car payment on a new car.
To me it's been reasonably reliable for an 8 year old car with over 100K miles on it and never left me stranded which is more than I can say for my wife's newer MBs
