I bought the 2003 540i with the 6-speed manual transmission, which automatically gets you the sport package; and, for 2003 models only (in the US), also gets you the M-sport package, which includes front and rear fascia, 18" M-parallel rims with staggered tire sizes, along with a host of ///M badged goodies, such as shift knob, steering wheel, doorsills, etc. This is the closest thing you can get to an M5, and is in fact more rare; less than 1000 6-speed 540s were imported in 2003. My car is black on black and is absolutely beautiful. It has a lot of "presence" and gets a lot of thumbs up! Fast, comfortable, but "mature"...no boy-racer junk. Hope to keep it forever.
The ///M sport goodies; the fact that this is somewhat of a rare & unique model within the BMW lineup. The styling, power, & handling. Gas mileage 27-28 MPG on highway). The 2003 E39 body style is one of the most handsome Bimmers made; definitely has the "Executive Express" aura about it.
The DSC feature of the premium stereo is a joke...basically just a type of reverb effect. Also, most Bimmers have a cursed "clutch delay valve" feature, which can be maddening when you are trying to shift smoothly. This is easily removed/replaced, so not that big of a consideration.