I have about 1500 miles on my 3i sedan with manual transmission. Mileage is good - about 33 mpg around the suburbs. It's hard to not put your foot down (which is, of course, bad for mileage) - this car begs to be driven! First car I've had in years with enough leg room (I'm 6'2") - I don't even have to put the seat all the way back. Easy to set up a good driving position with the adjustable steering wheel. Transmission has a nice feel and short throw. I have found the A/C more than adequate for my area (Virginia). Big trunk and lots of little cubbies for storing stuff (huge glove box).
Going into an uphill, 270 degree interstate on-ramp in second gear. YeeeHaaa! Getting 33+ MPG (as long as I drive conservatively). Front seat room and driving position.
I agree with the others that the stereo system is weak. I had just upgraded the stereo in my old Civic Coupe prior to giving that to my teenage daughter - her system definitely sounds better than the system in the Mazda.
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