I've had a '06 and a '07 and both have been relatively cheap to maintain. Nothing out of the ordinary by any means. Don't own the car if you cannot afford to and I second ndukyh's comment on finding it strange what some people complain about... But then again my other cars have been mostly Italian...
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'09 525xi | Comfort Access, Moonroof, Softclose, PDC, CIC upgraded
'07 335i E90 (sold) // '03 Porsche Boxster (sold) // '07 Alfa Romeo GT 2.0 (sold) // '06 325i E90 (stolen) // '99 Alfa Romeo 156 (sold)