I bought my Mazda3 after owning two Honda Civics and a Toyota Corolla. The Mazda feels like a race car in comparison: peppy 2.3L engine, strong 4-wheel disc brakes, quick steering, precise clutch/ shifter, and firm suspension/tight handling. I plan to drive my car in autocross races -- its handling is that good. On the flip side, my Mazda3's build quality is poor compared to Honda or Toyota standards. After just four months and 5,000 miles, my car has more rattles in the dash and doors than one of my Civics had after eight years and 110,000 miles! My car's fuel economy (2.3L engine/manual trans./moderate throttle) has been 25-27 mpg city (A/C on) to 30-31 mpg city (A/C off).
Sport-sedan driving dynamics, clutch/shifter, seats, gauges (esp. at night), steering wheel stereo controls, headlights, hatchback utility (including compartments under cargo floor), large glovebox, exterior styling, basic warranty (4 yrs./50,000 miles), and lower insurance premium than Civic.
Improve the interior build quality/materials, install less dusty rear brake pads (they're made from a cheaper material than the fronts), and increase the fuel economy of the 2.3L engine.