I have a 2005 Mazda3s 4-door with 156,000 miles. It's been fantastically reliable. However, it has *serious* rust issues. I already paid $900 to address rust-through on the B-pillar of the rear passenger side door (before I discovered that the car has unlimited mile coverage for rust-through for five years--oops). Now, that same rust through is happening on the other side rear door in the exact same spot, and there is rust starting where the rear fenders meet the rear bumper right at the wheel well, there's rust all along the edge of the rear fenders (facing the tire, on the bottom/edge), and when I gave it its first hand wash and wax for this year Saturday, I noticed little spots of rust along the bottom quarter or so of the doors.
So, on one hand, the car has been insanely reliable, mechanically, for 4.5 years and 156,000 miles, but on the other, none of the other cars I've owned (1991 Escort GT, 1997 Ford Contour SE, 2001 Focus ZX3, 2005 Honda Odyssey with even more miles on it than the Mazd3) ever had even close to this much rust. All of them were very high mileage cars (the 1991 Escort not so much with 106,000 miles at 6 years when I sold it). The Escort was just starting to show a little rust on the front edge of the hood in the center and some on the hatch (not visible on the outside), the Contour, at 206,000 miles had just a hint of a bubble under the weather stripping on the rear passenger side window, and the Focus, at about 4.5 years and just a bit less miles than the 3 has now had not even a hint of rust starting anywhere.