thought I'd add to the discussion.
I have a 57 320i (December 07 with ED). Have been reading this thread with interest and up to last week thought i had been one of the lucky ones.
Anyway, last week I got the Engine Warning light. Have to say that BMW assist were excellent and got to me in about 40 mins. Ten minutes later had changed by Cam Sensor there and then and it has been fine since.
Am on about 3k miles at present.
Apart from this sensor the car seems to be fine - no shaking or stuttering at low revs, smooth power, and decent mpg (about 32mpg around town and 38-44 on a motorway stretch) - but having followed this thread and having experienced the dreaded limp mode - it does dent your confidence in the long term reliability of a 26k+ motor. Just see to be waiting for another warning light to come on !!!