Here is my F30 318d sedan experience. I apologize for my bad English.

Engine
The most important thing about this engine is consumption. In my case after 50 thousand miles the total average is 54mpg. I drive mostly on country roads and highways, sometimes in moderate speed and sometimes fast and sporty. Only around 10% is in city.
If I really push the engine the average consumption increases by around 10%. On the other hand, when I really tried, I got a country road average of 95mpg. I would say that's pretty good.
Performancewise the engine is modest but in normal everyday driving I don't feel any drawbacks.
It produces typical diesel sound and is moderately loud but on speeds above around 45mph I don't notice it anymore.

Drivetrain, chasis, steering
Absolutely wonderful. The steering is extremely precise. The suspension is agile and sporty but still comfortable.
The DSC is better than ever. I had two 325i coupes in a row before and the E92's DSC was lightyears ahead from E46' but the F30's is even better. It is smart and quick and if you put it in sport mode it won't interfere to much.
Brakes are a bit too weak.
Alltogether the car is nimble, agile and precise and yet the ride is comfortable and pleasant. A bit too much windnoise though.

Interior
I will not talk about how it looks.
Materials are absolute r******. A lot of noises and rattles that the workshop was unable to fix. Rattle behind tachometer, in locking buttons in all doors, somewhere above my head to the left...
The central display is very small and looks cheap in basic version. Also does controller (iDrive) button. So pay for satnav or some other thing to get better looking display.
A noise in the driver's seat can be heard in every right corner. It sounds like a spring in an old couch.
All in all, very not-premium. Audi is much better. Even VW or Mazda. Even anything, I would say. Except maybe Dacia.
Spacewise... Better buy Audi.

Electronics
The essential stuff (DSC and engine electronics) is perfect but all additional stuff is disappointing.
Bluetooth interface crashes at least once a week. It freezes the computer screen and the iDrive controller becomes unresponsive. Only thing that I found helping is turning off bluetooth on my phone. Then the BMW screen reboots. I tried with three iPhones, two Samsungs, One HTC and one Sony and it did not help. I tried forgetting devices and then reconnecting them. I tried going to BMW for a year and a half every two or three weeks. I gave up in the end.
Harman/Kardon HiFi is worse than ever. It seems to me that the amplifier and loudspeakers are very good in fact, but the source (DAC I suppose) is r******.
The xenon headlights are otherwise fine, but the high beam is cut similarly like low beam, just higher. Never seen such thing before. I understand it maybe puts more light on the road but it creates a bit claustrophobic atmosphere.
The main display software is very inconsistent. E.g. if you shift to reverse it will display the car with surroundings and obstacles. Then, when you shift forward again, it will return to some random screen, not the one you were on before shifting to reverse.
Parking sensors will stay on even after you have shifted to neutral. This means they will beep continuously if they see an obstacle. Very annoying if you are waiting with the engine turned on. You have tu turn engine off and on to stop the beeping sound.
The light sensor does NOT detect tunnels. At least not for the first two or three hundred meters after you have entered a tunnel. Other cars detect tunnels before you enter them.
The rain sensor is the most ridiculous electronic appliance I have ever seen. I think it wipes randomly which ever setting I choose. It would be better to manually adjust intervals. Went to the BMW and they say it is just the way it is. If there is any way of avoiding equipment package with the rain sensor, do it. And, by the way, the auto-wipers light is on the right lever behind the steering wheel and can not be seen from the driver's position.

Tyres
Run-flats. Most people complain about run-flats, but I find them excellent. Be careful to buy star marked tyres - it means they are produced for BMW. You will complain otherwise. Avoid Bridgestone - they project too much to the steering wheel and you won't be able to keep the car straight on bad roads. Michelin and Continental are much better choice.

Summary
Nimble, agile, fast, precise, very good cunsumption figures. Essential stuff is just excellent. Everything else just sucks. Extremely poor experience with interior materials and equipment, much worse then older BMWs.
After being in love with BMW for 15 years I am now considering Mercedes, Audi and Lexus.