The brakes have been replaced twice.
The clutch has been replaced twice.
The water pump has been replaced.
The driver's side window motor and grips went bad, and were replaced.
The rotors have been replaced.
The ball-joint broke.
The front springs cracked and broke.
The automatic seat belt motor is going bad.
This car is a very sporty car and gets 30 miles to the gallon, 40 on freeway.
However, the MX3 is very expensive to repair and is time to retire only at age 10.
I was curious about your problem with the automatic seatbelt motor. I have owned my MX3 since it was new and started having problems with the seat belt while the car was still under warranty. It would intermitently lock in the restraining position, particularily during cold weather. Unfortunately, it would never do this at the dealer, so they were unable (or unwilling) to find anything wrong with it. Overall, my maintenance costs have been low and I have been happy with its' performance.
There was a recall for that issue. I have the same issue and it was already looked at by dealership in 2000 (previous owner). The dealership does not want to fix it for free, but I did call up Mazda and they said they could reopen the recall case and have the issue resolved.
I own a 1993 no problems at all with it so I must be the lucky 1 I think.