I bought my Estoril Blue M3 over one year ago, and haven't looked back since. The performance (acceleration, braking, handling, etc) are self explanatory. It IS a perfect balance of weight, luxury, power, and suspension to create the most pleasurable driving experience. The only thing that can top it, is the E46 M3. For an enthusiast, an E36 M3 is a car that needs to be in your garage.
The engine (S52) is wonderfull. However, the E46 M3 uses the S54 which is an upgraded version of the 1995 M3 (S50 B32 engine). The difference is, the S52 is more of an upgraded 328 while the other M3 engines is a stand alone (individual throttle bodies for each cylinder).
Nothing comes to mind other than a more simple electronics design. The electronics are OK, however, it does have room for improvement. Stock U.S. lights are a joke (spend $600 and get a set of HID+halos).