As a related but side issue, I drove the new 428i Coupe yesterday at a BMW dealer "drive" day. Only a brief 20 min drive, little urban and some more open hiway. I was impressed with the power, and quickness, of the N20 in the heavier 4 Series. They did not have a 435i on hand to compare to. Regardless, the 4 is not a car I would buy, too large for my tastes.
Would I get the N20 in the 2 Series? Maybe, I would have to drive it first; BUT I would be more likely to get the N55 a la M235i just because one can never have too much power
I think the N20 is a very good engine, and may make for a better DD than the larger engine, for some ppl.