When I bought my 750Li I was very excited about it. The styling has grown on me over the years and the interior was very comfortable. Now that the car is almost a year old I kind of regret buying it, though. It performs like a dream and certainly has all of the features I wanted, but the quality of interior materials is well below that of its competitors and reliability problems have been unending. So far everything has been covered by warranty but I am afraid of what will happen when that ends. All in all, it has been just like all my other BMWs, very satisfying to drive but not to own. I think I might make the switch to Mercedes-Benz or Audi after this.
Scrap iDrive in favor of something more intuitive, use real wood and better quality plastics inside, improve overall quality (a great performance sedan is no good if it spends all its time in the shop).