when I first got my 320d, i absolutely loved it. Then the motorplan expired and everything started going wrong. It ran up a 30k + bill in the space of 4 months thanks to injectors, engine mounts, propshaft coupling... The list goes on.
I traded the 2002 320d in at 166k on the clock, and bought my current 2003 320i at 92k on the clock, 3 yrs later it now has 144k on it and has cost me a total of just on 10k, including the cost of new brake discs, tyres, radiator, waterpump, vanos seals, control arm bushes and some other stuff. I'm actually scared to trade this car on something else for fear of getting another money pit like the 320d.
It seems to be a mixed bag when it comes to the E46 320d, but experience tells me that there are more negative than positive experiences with them, and I dont know if you willing to take the gamble on getting one of the good ones. I would personally get a 325i or 330i, and smile everytime you put petrol in, because you know that the extra it costs you now, will save you big in the long run.