I have been in 2 serious crashes in Mustangs, and both faired quite well for the circumstances.

#1 was a fox-body going 50mph into the side of a Crown Vic (T-boned). I walked away with a lumpy noggen (hit the windshield/sunvisor), a bruised knee, and an incredibly sore body. The car was a total loss, but it took the impact incredibly well.

#2 (3-months later) was in a '97 Cobra Convertable. I was rolling at about 15mph and some dude going about 40-45mph slammed into the back of me. Damage was a bent steering wheel and the entire rear end of the car shifted forward and to the right a few inches. No injuries, no fires...I even drove the car home.

Granted the Mustang isn't the safest car around...but I would never feel unsafe driving one.