Its competitors are impressive, but the 2010 Mercedes-Benz S-Class remains the definitive premium luxury sedan. Standard equipment on the S400 Hybrid includes 18-inch wheels, air suspension and adaptive damping, automatic wipers, a sunroof, automatic headlights, power-folding heated mirrors, a power rear sunshade, a power tilt-and-telescoping steering wheel, dual-zone automatic climate control, 14-way power front seats, front seat memory functions, heated front seats and leather upholstery. Also standard are Bluetooth, a navigation system, the COMAND electronics interface and a 14-speaker Harman Kardon stereo with six-CD changer, auxiliary audio jack, an iPod interface, HD radio and satellite radio. The Premium 1 package adds adaptive bi-xenon headlights, LED daytime running lights, adaptive high beams and ventilated front seats. The S550 comes standard with the Premium 1 package but is otherwise equally equipped. Fitting the S400 and S550 with the Premium 2 package gets you upgraded front seats, keyless ignition and entry, front and rear parking sensors, and a rearview camera. The 2010 Mercedes-Benz S-Class comes packed with antilock brakes, stability and traction control, front and rear side airbags, side curtain airbags and a driver fatigue and inattention warning system.