The Fusion is a totally separate all new car, and not related to the Five Hundred at all.
I've posted this before - the Fusion and its corporate siblings the Milan and the Zephyr/MK Z are excellent cars (as reviews and consumer reports agencies have shown). I still don't know why Ford hasn't been promoting the fact that the Fusion has been scoring better than the Camry in multiple venues.
The Five Hundred is a continuation of the old Taurus line and it really is a POS. Most of the Tauri in rental fleets were under 20K old. If you got one with more, you got to see just how badly and just how quickly they decayed.
Really,
And so is the Volvo it was sprung from? Go drive the revamped 08' model.