Two vinyl tops, about to get a third.
Driver's side window motor.
Cloth seats wearing (on second pair of seats)
Repainted car in 2007 - faded irregularly (but was also in a few minor fender-benders and the body shop didn't always match colors well.
Have replaced minor plastic parts (ashtray top, map pocket on door)
Generally I use Mid County Mustang on line for replacement parts - very complete assortment.
Just purchased hardtop.
Top leaks in heavy rain - was not well designed.
Poor interior light at night unless you have the hardtop.
First off, I am sentimentally attached to this car as it was my late partner's primary car in California.
It has worn quite well considering its age and that it was an inexpensive car to start out with. I've kept it very well serviced by a local mechanic wherever I lived and they seem to be able to easily address relatively minor issues that came up. More recently I have invested in a hardtop for it (purchased on Craigslist) with other parts from Mid County Mustang on the web or Capri Parts also on the web.
The car is definitely cheap to run - I have the 5 speed manual transmission, which is fun to use - and I average 33 miles to the gallon (range 25 - 39 mpg).
I love to drive the car in the summer - it is a little skateboard with agility and speed. But of course, it is small so I feel a little intimidated when an over-sized Cadillac Escalade starts to tailgate me (yeah, I am one of those guys driving 55 mph, but always in the far right lane).
It is cool to own and drive a less commonly-seen car, and now that it is winter the hardtop gives it an much sportier look than with the old vinyl top up.