As noted in other responses, the 626 model suffers from serious tranny issues. Mine suffered a failure when I got it. Turns out it is a widespread failure and a replacement tranny is hard to find at junk yards, because they are all blown.
There is an overheating issue which damages the tranny fluid which causes the tranny to fail. I think these cars have Ford trannies in them. This affects both 4 cylinder and V6 models.
I installed Hayden 404 cooler, which is supposed to be the greatest for 626 and thus far put about 15K miles with no problems. Will be interesting to see how long it lasts. When the second tranny failes, I am not going to fix it. Nor am going to put any serious money in it for any reason.
It's clear that if you want a 626, a 5-speed is the way to go. With V6, it's nice.
I also had other random annoying issues, but all in all, it is a nice performing vehicle. For a V6, the mileage is very impressive, I get 29mpg on highway only on cruise. 2.5L engine is nice, aside from oil leaking into the spark plug area. It's the nicest performing vehicle I've ever had, and handling is superb too.
One serious downside, the engine bay is kind of tight. Timing belts took me 6 hours to do. Though I am sure a Mazda mechanic can do it in 2 or less. But the engine bay design is poor: The fuel filter replacement is a big job for example. Took me 1 hour to do.
The previous car I had was a Chevy Caprice and in terms of reliability and quality, it was way higher. It had much higher mileage without all these issues.
I really could not believe when I broke a strut in this Mazda when hitting a minor pothole. I didn't know this was possible.
I would buy only a 5-speed one, with low miles and if it has been well-maintained - for a good price. They don't hold their resale value at all - for a reason. I also hear that 4-cyl. with manual get awesome MPG, something like 40mpg.
Also, the Factory Service Manual is a good investment with this car, you'll need it.