I have an e90 325i. I have to agree with the fuel consumption. I average approximately 600KM per tank. Sometimes I get more. On long distance with cruise control I can get up to 900KM per tank.
I recently bought an aFe intake since then I am yet to get better than 550KM. That's only because I rip it everytime...lol. I drive approximately 70KM to and from work. I am good with a tank of gas all week.
If I drive very conservative I can get better than 600Km/60L. Overall it is a great car. When it comes to servicing take it to a local shop instead of a dealer. You will save alittle.