I drove a f30 328i for the first time this week when my e90 M3 was in the shop. I always found the e90 328i loaner cars from my dealer to be very engaging and fun to drive, and recommended the car to numerous friends. They all love them.
I'm not so sure about the f30. On the plus side, the structure is very solid and feels great. It's also very light on its feet - feels lighter than the e90.
The N20 is a real gem. It has great power and torque. Its not quite as smooth as the N52, but the power is tremendous. Coupled with the 8 speed auto, it was a very flexible powertrain. (I'd get a 6 speed if I was buying it for myself.)
Two things affect my overall impression of the car in a negative way. The first thing is - I can't stand run flats. The car I tried had the base tire, and I could tell they were run flats - more noticeable than on my F25 X3 with the dynamic handling package.
The second thing, and the thing that they must fix - is the steering. Even in sport mode, the steering had no life to it. The car seems capable, you just can't feel it through the feedback in the wheel. I always thought that BMWs were "worn" as much as "driven". They seemed a natural extension of the driver's body. The steering feedback and feel was a key component of that feeling. The F30 just wasn't that much fun to drive - something I never thought I had to worry about with BMWs.
I hope they fix this before I have to replace my E90. I might have to shop around if they don't.
2008 E90 M3 - Dinan Stage 3 and BBS CH's
2000 328i sedan (UUC suspension - still the favorite)
2012 Mini Cooper (wife's)
1991 325iX (sold - gone but not forgotten!)
2014 X5 35d (Performance Center delivery May '14)