I had rented a 2005 5 series wagon while in Europe and put nearly 3,000 km - wanted one ever since! This car has a gas engine, AWD and a few more options but the same body and feel. It's clear to me that BMW builds a better vehicle than most. I have owned 37 cars in my life so far and this is indeed at the top (second only to my Boxster) when it comes to fit, finish and feel. The handling is superb, the seating position very comfortable, and power is adequate. The 255 hp is enough but, as is the case with every car, it slowly becomes insufficient as one gets to know the car well. The auto trans is very nice and the Sport mode is great. Good on gas if you don't get too aggressive ;-).
Handling (for a big car it is fantastic), Swivel xenon headlights, Sport mode, quiet, Panoramic sunroof, Harman Kardon Logic7 sound (wow!), heated front and rear seats. And I think the iDrive is just fine. Clearly people who complain about it must be used to very basic cars indeed.
Power lift gate close command on remote or dash (one has to push a button on the gate itself). A little more tilt on the power seat.