I had a 2003 525i and thought it was a nearly ideal vehicle. This car, however, is almost perfect. It is roomy for long trips and hauling children as well as for looking really "cool" on the road. Low maintenance costs. The iDrive is very simple to learn, even for those who aren't very technological. Other brands can't compare to BMW!
Sirius radio, warranty, styling.
Slightly sportier handling, better front cupholders (although great improvement over prior generation of 5 series).