I bought my Mazda 3 brand new 7 months ago, and don't have a single regret.
I love the handling, and wanted a manual, but decided an automatic was better suited to my long commute which often leaves me sitting in traffic.
Everything has worked perfectly, and other than routine maintenance I haven't had it to the dealer for anything.
Great interior, headlights are great at night, very fuel efficient despite reputation for not being near the top of class (consistently best the hwy rating with mixed driving), hard-to-beat handling/fun-to-drive factor.
Would be nice to have a more up-to-date screen/interface for radio, etc.
Looks dated and isn't space efficient. Otherwise I wouldn't change a thing.