Is the BMW 3 Series really unreliable and expensive to maintain?

It seems there are lots of dissatisfied BMW 3 series owners (going by comments on various consumer reviews). Is there any statistic showing the ratio of dissatisfied versus satisfied owners in the USA? My thinking is that consumers with horrific experiences are twice more likely to vent their frustrations via various feedback/review systems than satisfied customers echoing their positive experiences via the same medium. I'm interested in buying a 2002-06 BMW 325 or 330.