Motor Trend's review of the Audi S8 focuses on its dual personality as a luxury limousine and a capable performance machine. The editors note that the S8 accelerates with "violent smoothness," crediting the eight-speed automatic and Quattro system for seamless power delivery. They are particularly impressed with the optional laser headlights and the rear-axle steering that makes the large sedan feel more maneuverable in tight corners. However, Motor Trend criticizes the S8's steering feedback as somewhat numb and points out that while the air suspension is brilliant, it can feel floaty at high speeds in Comfort mode. The interior receives high marks for build quality, front seat comfort, and the Virtual Cockpit digital display, though backseat space is noted as merely adequate rather than limousine-like. Fuel economy is poor, as expected from a V8 in this weight class. Motor Trend concludes the S8 is a superb grand tourer but not a true sports sedan, earning a 4.0 out of 5.

Kelley Blue Book's review of the Audi S8 scores it 4.2 out of 5, calling it "one of the most refined high-performance sedans available." KBB praises the combination of the 563-horsepower V8, standard Quattro all-wheel drive, and the optional active suspension that uses cameras to anticipate road conditions. The review notes the S8's interior is beautifully appointed with premium materials and exceptional noise insulation, making it nearly silent at cruising speeds. KBB highlights features like the massaging front seats, head-up display, and the advanced driver assistance suite, which the editors describe as "among the best in the business." They caution that while the S8 is exhilarating in a straight line, it lacks the steering feel and chassis feedback of performance rivals, and the infotainment learning curve is steeper than competitors' systems. Residual value is also a concern given the luxury segment's depreciation. KBB ultimately recommends the S8 for executives and enthusiasts seeking a discreet, fast, and supremely comfortable daily driver.