I can only share my own experience with my gen 1 2006 Mazda 3, which was bought brand new.
Overall I like this car very much, even better than my 95 Accord 5spd manual, which was an excellent car. It driver very nice and is quite responsive, also the 4spd slushbox is programmed surprisingly well and does not hesitate to downshift without flooring that car.
I have the 2.0L engine and it has almost 130k miles. There is a minor weep from the timing chain cover, but despite this the oil level doesn't change between 5k mile OCIs.
Over the years it needed the top strut bearing twice, both covered by the warranty. The second one failed within a year of the first replacement, so I suspect either a bad part or sloppy installation. The second replacement is doing great to this day.
For some strange reason, the serpentine belt tensioner pulley kept making noise and I replaced it several time already, but I think the tensioner itself is not aligned properly with the rest of the pullies so I will change the whole thing.
Other than that, only this year I had to spend a more substantial amount on the car. I replaced the struts and the front wheel bearings (only one failed but I decided to change both as the car will be kept for few more years).
Regarding rust, well it is not good and although my car is clean because I was very diligent about rust proofing, however despite all my efforts, the area around the third brake light, which is located on the trunk, is starting to rust and I think the window frames on the doors also start to bubble up. I can handle this of course, but it should not be happening on a car that is not yet 10 years old.