In fact there have been lots and lots of reports. The latest Safety publication, which records all ASRs and MORs, had about fifty reports of cockpit fumes, outnumbering all other problems put together. They made a lot of noise about fixing the problem. They reduced the amount of oil carried in the engines and replaced a couple of the really bad engines but there were still incidents happening several times a week as of last week. An incident can be anything from a "Bad smell" to "intense fumes". It's very subjective and by all accounts they're never visible.
As the previous poster mentioned, there are some airplanes that don't smell at all, so the problem must be just in the defective engines, but after two years of listening to their promises about fixing them I just got tired of waiting and decided to vote with my feet. I hope they do fix it. It's incredibly dangerous both in the long term and in the short term. More than one pilot has been virtually incapacitated, fortunately the worst of these was on the ground. The consequences of both crew being affected by a major fumes incident, well let's not go there.
Just as worrying are the long term effects. Quite a few of the airplanes put a low level of fumes in the cockpit on every flight. Just a smell, but an unpleasant one. It means one is being continuously exposed during the entire flight. Some don oxygen, others just put up with it and still others can't smell it at all. The airplane is usually grounded for a while, given a compressor wash and sent back out again, sometimes with one pack deferred as U/S, other times with the problem cleared, until the next time it happens.
As I've said, this isn't my problem anymore (I hope!) so this is my last word on the subject.
Best of luck to all there, none of them deserve this.