I'm looking to move from an M57 330d to the 328i touring (wagon), so again had reservations on the engine ability to feel solid.
I know some would feel after the 6-pot diesel the petrol would be a let-down. But remember I had a V8 (E39 540i) and loved the silky smooth feel of the engine and transmission. OK, not a true comparison, but the softer feel and adding a few revs in the petrol, rather than the harder edged feel of the diesel is not miles apart, for normal driving. The 328i does have a decent mid-range, so not a flat engine, lacking torque. Will suit my driving conditions and the power is there for the overtaking when needed.
The other reason for me looking to the 328i, I'm a low mileage user these days, in the BMW, and many of the trips are only about 12 miles. So not good for a big diesel with the DPF regenerations and all the other issues of cold running winter time.