The Mondeo TDCI is by no means a ticking timebomb or "riddled with expensive problems".
Every time someone asks about these, I say the same thing so I'll say it again this time.
The Mondeo, generally, is a very reliable car and the TDCi is no exception. The 2.2 actually manages fuel economy thats nearly as good as the 2.0 and the servicing costs are the same.
There are 2 problems with these that are relatively common and have given the car this stupid reputation around here.
The first is the flywheel - a failure of this is almost entirely due to how its been driven and how many mile's its done. I'd be looking for a relatively low mileage car on its first or second owner, and more importantly get the current driver to take you out in it. If they cant drive smoothly, labour the car in low geers etc and its done most of its journeys around town then its probably not got too long left. There's plenty of these cars about so walk away if you're not happy. Rattling at idle, struggling to start and a squealing clutch tells you its already on its way. If anyone tells you its going to cost £1200+ to fix, laugh in their face. Mine needed doing and cost £650 - yes, thats still a lot of money but its literally all thats gone wrong in the 18 months I've owned the car.
Secondly, injectors. The same point applies here about how the car is driven - if they needlessly rev the nuts off it, have a "tuning" box installed then walk away. Try to see the car when its cold - if it smokes when its starting then one or more injectors are on the way out. Contrary to my advice above, push the car to the red line when you try it - a lot of cars where the injectors have gone pop will go into limp home mode here with a flashing glowplug light. Again, people will spout crap about them costing more than a grand to replace - ignore those people too. A full set of 4 genuine delphi injectors can be ordered new for 300 quid and its an hour's job to fit them.
So, why bother then if there are these 2 problems and other cars that don't? I'm not going to get into the petrol v diesel argument, its been done to death and it never goes anywhere. However, the 2.0 TDCi 130 is a much better drive IMO than the 2.0 petrol, plus youve got the added bonus of better economy. Servicing isnt more expensive on the diesels at main dealers or independents either.
When you're looking at other cars, you have to consider how reliable the Mondeo is generally. I've had the flywheel replaced but thats it - £650 in 18 months (excluding servicing) is really quite cheap, you could buy another car and it might cost you £100 in a little repair every month.
The Mondeo is one of the best cars in the class and is brilliant value for money, if you're after a car like this then the Mondeo's the one to go for - just be rational about the petrol/diesel comparisons. If the car's been looked after and not been driven by an idiot, it will serve you well.