The 2007 model also includes less visible mechanical changes. The keyless entry system was improved. Reinforcements to the body shell improve overall chassis rigidity. The front dampers of the MacPherson strut suspension have been re-tuned to quicken steering response and reduce understeer. The hydraulic dampers of the multi-link rear suspension were also re-tuned to match the front suspension changes. Mazda engineers and designers addressed concerns regarding cabin noise level by redesigning or changing multiple systems and adding sound-deadening material to the roof lining and hood panel.
I was also told that the 2007+ models had more airbags added.
2006 Mazda 3S Sport - Making it the best that it can be