Audi's top-level sedan delivers smooth and effortless acceleration yet attains commendable fuel economy even with all-wheel drive. The car handles crisply and holds the road tenaciously, making it one of the sportiest luxury sedans we've tested. The ride is firm and steady but not as cushy as in the Mercedes-Benz S-Class. Interior ambience, quality of materials, and craftsmanship are top-notch, and the cabin is quiet. The front seats are exceptionally comfortable and supportive, with a variety of massage settings. The rear seat is worthy of a limo, but the trunk is a bit small. The infotainment system takes some getting used to but proves logical. The base supercharged V6 has ample power, but the 4.0-liter V8 turbo is a powerhouse worthy of such a flagship.