The 220D was Lexus' first venture into the salesman's car market & I think it is telling that it has not been followed by any other diesels and it doesn't look like there are any in the pipeline. Whilst it is my view that the 220D is the only nasty Lexus with an engine whose characteristics do not match the gearbox etc. very well; this is from the viewpoint of their superb petrol cars - and particular their automatic transmissions. The downside of the reputation of the 220D is much because its users spend huge amounts of time driving them, and thus notice every fault & foible - many of which are generic to diesels.
What I think is clear though is that the 250 auto MM is the Lexus 2 series car of choice unless you really need the extra economy of the diesel and are prepared to sacrifice everything else in its favour. Other manufacturers have concentrated much more on diesels and unsuprisingly have produced better ones - but I would caution that this only means that they are slightly less unpleasant to drive.
I believe the diesel is an evolutionary dead end in cars, and a good idea is to stick to petrol until newer emerging technologies mature.
i love mine but my only gripe is with the poor economy for a diesel, and the usual 1 to 2nd gear change. however the first time i am in a position to change it, it will be bye bye 220d and maybe hello to the 250.