I've got a 2015 2 litre diesel auto 4x4 with nearly 56,000 miles on the clock. The car easily achieves high 40s mpg in mixed motoring, and over 50 at relatively constant speeds on the motorway.
If the price is right and you like the car I would say "buy it". Mine has the 6.5" Nav screen and my only gripe there is the expensive cost of map udates, so I don't bother, I bought a top of the range Garmin, it was cheaper.
All in all I love it. I'm hoping to change my car soon and normally I wouldn't hesitate to buy another but I shall be defecting to another make simply because Fiat no longer offer a diesel, automatic 4x4 so I will swap to a make that does. I have had it for over 4 years year and it has been right up there as one of my favourite cars.