Poor reliability.
No good for fast driving. Won't do more than 65 mph!
Rusts very easily.
Massive engine faults like burning oil, leaking oil etc.
Rubbish, never going to buy one again.
If it won't do more than 65mph it is either in a very bad way, or in serious need of a tune and service. I know that performance is a problem with many mk3 Fiestas (I own one myself), but they should be able to do high 80's mph (according to the manufactures figures, backed up by my personal experience of being overtaken swiftly whilst doing 70ish on the motorway)!!
My 1.4i 1990 Fiesta LX will do 126mph.