I purchased my 2007 530i new 2 years ago; I traded my 2004 530i in when I reached 45K miles. I have not been disappointed with either of these cars! The handling, comfort and power are great. I test drove a 2004 525 when I was first looking because the dealer had one with the Sport Package but I chose the larger engine and didn't regret my choice. The 50K no charge warranty is great but honestly, the dealer makes things up so they can fix my car, e.g., change the wiper blades, etc; I have not had any real issues with my cars.
Power and handling, MP3 CD player, steering wheel controls and the warranty.
Cup holders are a joke but they do work; I rarely use them. Minor trim issues such as black coating chipping on certain parts; dealer replaced all of these for free.