Driving around Sarf London/N Kent:-
F30 (62 reg) 320D: 43 mpg
E90 (59 reg) 320D: 41 mpg (still in family)
F30 seems more nippy, smoother ride, better on corners and firmer around fast motorway curves. F30 maybe a bit noisier in the low down gears.
Yes! The F30 is an improvement on the E90 but the E90 is still a nice motor to drive!