I've owned a few BMWs over the years, although the latest one is a 2003 330i ZHP. Other ones that I owned were a 94 325i, a 98 M3 convertible, and a 2003 540i M-sport, all with manual transmissions. I've driven every new generation of 3 series and 5 series available in the U.S. since 2003, and didn't find any of them satisfactory from a driving experience standpoint. Every time, they came up wanting compared to my 330i. Some of them were faster, smoother, and more luxurious, but when it came to handling and driving pleasure, my 330i was just plain better. I've also driven the competition from Mercedes, Audi, Lexus, and Infiniti, and again I preferred my 330i.
The Model 3 is the first sports sedan I've driven in the last 15 years that I find to be more fun to drive than my 330i. There's only a couple of things for the driving experience that I prefer on the 330i: the steering feel is a little better and the car is physically smaller making it a little easier to place it on the road. The Model 3 beats it in every other regard: instant throttle response, steering quickness, better brake feel, AWD to power through and out of the corners, better ride, quieter, and roomier. It kind of combines the ride and luxury feel of the 540i M-sport with the handling and responsiveness of the 330i, while having a roomier interior than either, and being significantly faster than either.