I've got a 2012 (facelift) 3.0 XF-S - just turned 100k on mileage and cant fault its reliability. Only wear and tear items, tyres, brake pads and discs and one stop\start battery replacement but that only cost £30 from internet shop and not the £300 Jag dealer wanted!!
Its a great car but as with all things like this, best to get an independent check done on it to make sure there isnt anything nasty lurking to catch you out.