1997 E300TD here, engine is rock solid.

Likely problems:

Glow plugs (have a habit of snapping off and remaining in the head when you change them)
Belt tensioner (not a big job really, mine went at 160,000, couple of hundred £'s to repair).
Fuel pipes (very easy to fix, although nothing wrong with mine)
MAF (very common, these fail regularly although they're easy to clean and replace)

In English money, I get 40mpg on the motorway, 0-60 in under 9 seconds, and the engine is very quiet right up to around 90mph.

/edit: milage = 170000