I traded a 2003 Chevy Silverado in on this Mazda 3 5-door because the Chevy truck was the most uncomfortable vehicle I've ever owned. The Mazda 3 has a 2.3l inline 4-cylinder that has quicker zip than even my 6-cylinder truck had, and 30 mpg highway isn't bad. The drivers seat is very comfortable and all the controls are very easy to reach. I strongly recommend the 5-speed manual transmission for the most pep. Visibility is awesome in this vehicle. I drove a Toyota RAV4, Hyundai Tuscon, Mitsubishi Eclipse, Honda Civic (my second choice), and a Dodge Caliber before finally deciding the Mazda was the best choice. None of the other vehicles even come close in performance and visibility.
The pep and quickness of the 2.3l engine is my favorite. The body design is second. Back seat room is also pretty good. Not as good as my wifes Chrysler 300M, but the average adult back seat passenger has enough room for a comfortable ride.
Room in the hatch could be a little better. I have to fold down one of the seats to fit my golf bag, although I wouldn't compromise back seat legroom. Air conditioner could put out a bit more cold. It's cold enough to provide comfort in 95+ degree heat, but it takes a while to bring temp down.