The face-lift ones (post 2012) are VAGs 4th stab at getting that model right and theres pretty much nothing model-specific they goes wrong with them. Diesels seem bombproof so far (common rail, not the PD ones the A4 got) I don’t know much about the petrol ones other than they’re fast – it’s the same engine VAG uses right across the range so faults should be well known.
As for the car itself, they’re great to drive – it’s got A6 dervived suspension so rides and handles better than when it was an A4, they generally get loads of kit, my diesel has got dual climate, leather, sat nav, Bose, reversing sensors etc etc.
Downsides, the boot isn’t massive for an estate, it’s smaller than the saloon boot for example, there’s not a huge amount of leg room in the back.
Oh and the depreciation, they’re not well known and people won’t pay a huge amount for them – we paid 12k for mine a few years ago – it was parked next to an older A4 estate, without half the toys, more miles and the PD engine, that way 14k.
Great news when you’re buying it, a bit of a pain when you’re ready to change, it can take months to sell them privately.
Mine did Calias to Morzine, 4 up with bikes on the roof in 1 tank, I suspect a turbo petrol won’t 😉