I'm the second owner of my Mach 1, and I've had it for nearly 6 years with very little trouble.
The only thing I had to do to the engine, was changing out the thermostat housing after it sat in the garage all winter.
Brakes are very expensive, due to its exclusive brake/suspension package, and they were tough for me to change, probably easy for somebody who does brakes a lot.
The only big problem I had with her, was my transmission's overdrive going out twice.
This was due to the 4:10 rear end that the previous owner had in it....luckily it was a warranty repair and only $100 out of my pocket.
Other than that, it's the best handling stang ever made, and blows the doors off z28 and t/a's
Handling, and raw power...super impressive powerband that I've never felt in any other sports/muscle car.
Beautiful stock exhaust sound.
Still get compliments on it almost daily.
Only thing I wish it had, was automatic up/down windows lol