New TT/R8 sets the standard for modern car interiors. They're utterly flawless, every button gives the perfect feedback, just enough driver-focus on the cockpit without looking daft, and the new LCD customisable display for the centre clocks is a work of cohesive art.
996 is a dreadful design inside, but the quality of materials is immense. Pick up an 18 year old 100k mile car now and it'll look like it did when it was 1 year and 10k mile old. Merc seats are beautiful but their infotainment is garbage, i-Drive is better but still confusing, new Panamera is a huge step up and potentially up there with Audi.