Short in electric wiring that is still unresolved (after multiple trips to dealer and independent shops).
Convertible top leaks. Trunk leaks badly - cannot store anything in trunk.
Car shudders badly when launching.
Paint chipping / peeling on rear bumper.
Driver seat leather beginning to crack and peel.
This is a FUN, fairly reliable car for a person without a family.
For the price I paid, the car has met my expectations with respect to performance and "fun". I really enjoy cruising around with the top down and the excellent music system. The manual transmission adds to this and really makes for a zippy, albeit not truly high-performance ride.
Mechanically, I have found this car to be quite reliable. The engine and transmission are still quite strong and the mileage has been consistent with my expectations (25-26 mpg). I feel like I could easily run this car another 50k miles without serious repairs. It has never left me stranded despite some occasionally harsh conditions and treatment. My only mechanical complaint is the temperamental clutch system that shudders on almost every launch.
Outside the mechanical area, the Mustang leaves significant room for improvement. My convertible top has leaked for several years now despite repair attempts. The trunk also has a serious leak that renders it unusable during rainstorms. This leaves a musty smell in the car that is a little embarrassing. My car has a short in the wiring (presumably due to constantly getting wet during rain) that will probably never be resolved.
The interior quality is average. The back seat is a joke in all Mustangs and frankly not usable. The front seats look and feel reasonably nice, but are already beginning to show moderate wear. The door panels are worn and the driver side panel randomly broke without explanation. The plastic interior looks, feels, and sounds cheap and adds consider 'rattle' to the ride.
Overall, I enjoyed this car in my younger years due to its fun driveability and the convertible top. It hasn't failed me yet, but does have some quality issues. It's not a practical family car due to the cramped interior, but is great for a young (or young at heart) person.