Bought this new and have over 50K on it after 4.5 years. Only issues have been an LCD display problem (very recently at the 4.5 year mark so it's out of warranty) and the plastic around the lower end of the steering wheel column rubbing against something and sometimes "creaking" very low as you drive -- otherwise the fit and finish of the car was/is excellent. We avoided the 6cyl version as that was a Ford engine with noted reliability issues. Besides being a little underpowered, the 2.3 4cyl has been excellent so we bought the same the next year in our Mazda5 (which has also been excellent after 50K miles). Overall we've been very pleased with our Mazda6 "Sport" (hatchback).
Hatchback! 60/40 split rear seats + huge trunk carries tons incl 65lb dog+kennel, cat+kennel and our baby in the baby seat. Too bad hatch is not yet offered in the new 6. Front seats very comfy on long (8+ hrs) trips which is what orig sold us on the car after making a long trip in a rental Mazda 6.
Leverage Ford partnership to get the Sync as an option. Offer HID lights as well as adaptive lights (moves as you turn the wheel) as an option on the 6. Offer a hybrid in -any- true Mazda vehicle (the rebadged Ford Escape hybrid does not count -- I want Mazda reliability, not Ford reliability!)