I've had mine for 4 1/2 years as a daily driver, got it on 24k miles and it's now done 110k..
In that time it's been serviced regularly and apart from new injectors at 36k, done under warranty and an egr valve at 86k it's been fine.. Touch wood!!!!

The drooping rear bumper is a fault on all facelift models but do a bit of searching online and you'll find loads of info on it..
I have also had to replace the rear subframe bushes but they're an issue on most mk3 mondeos...
As for mileage I do a mix of town and motorway and I get 45-55 mpg all of the time.