The biggest killer of all of the Fords I've worked on has been rust. But in recent years they've got on top of it. Ford now has a 13 year corrosion guarantee on their vehicles.
The only mechanical problems I've come across was due to not servicing them. The turbo on a turbo diesel Focus failing because the oil was 40k old.
Although the Mk3 Mondeo has a rear subframe bush problem, it is no uncommon for them to fail and until recently (about 3 years ago) you couldn't get the bush on its own, it had to come with a new subframe. At about £1,200 a pop you can see why many people chose to bin their cars. But the bush is available for about £25 (not genuine Ford though, they still only sell it as a subframe last time I looked into it), bit of a shit to fit, but otherwise a better option.