I've had my '06 220d for just over a year now & despite some initial teething problems that got rectified quickly enough, I'm really enjoying it. It's a lovely place to sit & eat up the miles. IMO it's far nicer to drive than the equivalent BMW e46 320d or the A4 1.9/2.5 TDis. Seats are better, sound insulation is better etc.
The only disappointment really is the gearbox. It's a shame that the auto isn't more common over here. All the 220ds seem to be manual (not sure if it's actually available in auto??). I would agree with others that for speeds up to 80mph, 6th is pretty much redundant which means in 99% of daily circumstances it's uselss! At the other end of the range, 1st & 2nd both also seem to be a bit at odds with each other. 3rd & 4th though at speeds over 45mph are a pleasure & give great, torquey acceleration for overtaking.
I'll be the first to admit that because mine is on the road all the time, it doesn't see as regular EGR cleans etc., as it should. But it still gets 40+ mpg on the motorway which, considering it's 9 yrs old, heavy & a 2.2 with 160k miles on it isn't the worst, but it's not great either. My old '01 MKIV TDi would regularly see 50+mpg.
I am suprised though at the number of people on here buying diesel cars & doing very low mileage. To me it makes no sense. Unless you're doing upward of 20,000 miles a year, there's more value to be had in petrols I would have thought. The increased service costs & wear & tear items like turbos, EGRs, cats etc in diesels far outway any fuel cost savings below that mileage.
In Ireland (where I'm from & live) the Govt changed the car tax system in 2008 from a cc based system to a Co2 based system which meant that diesels suddenly became very attractive in terms of fuel costs & tax saving (a typical VW/AUDI 1.9TDi went from around €550 p/a to €256). The result is that there have been very few petrol cars bought since 2008, and there are people all over the country driving big engined diesel cars that are costing more to run than a 1.4 petrol equivalent that would probably better suit their needs. When these come on the market as trade ins, they are riddled with problems like clogged engines, manifolds, cats etc cos they never get properly used.
I drive 30+K miles a year with a normal daily commute of about 120 miles & the wife does the same in her car so makes sense for us to have diesels. For my purposes, the 220d is a great car & as I said, much nicer to drive than the equivalents. The complaints & disappointments expressed here seem to be mostly from people who might have been better off buying the 250 or something else altogether given their driving habits. Diesels on short trips are never going to be the more economical choice in the medium to long term. Just my 2 cents.