The upholstery is called M-B Tex and it looks more like leather than the real thing on some cars, wears well and is PETA approved; leather is available on any C.   Some cars have aluminum trim, others walnut or maple, and you can pop for carbon fiber on the C63 but whichever you choose it is the real thing.   Most of the trim, all the way down to the Mercedes-Benz badges in the front floor mats, is low-glare so errant reflections don't distract or dazzle the driver, and assembly quality is first-rate.  

Front seats are electrically adjusted with heaters available and with the tilt/telescoping steering wheel (powered, with driver memory as standard on C350 and C63) provide good support and driving position; those of larger sizes may find the Sport seats a tad confining while others will appreciate the lateral support.   Luxury model seats are less aggressively bolstered but maintain the hours-long support and comfort.  

Relative to some other ultra-performance sedan seats those in the C63 don't look overly racy and hard to extricate yourself from but the deep side bolsters and range of adjustments offer superb lateral support.   The C63 has aluminum shift paddles behind the steering wheel (upshift right, downshift left); a leather and Alcantara flat-bottom wheel is available.  

Cabin styling follows the same forward-sloping theme as the outside, with armrests that gently fall away forward and end in window switch plates angled parallel to the dash and center stack of controls.   The center console also slopes downward forward, adding control space to the vertical surfaces, and the dashboard arches downward away from the windshield adding a degree of spaciousness.  

Instruments comprise analog coolant temperature and fuel left, speed/display center, and tachometer to the right.   The speedometer needle rides around the outer periphery of the gauge, the center is a digital display used for the extensive information available though the steering wheel controls, and everything from oil temperature to directional instructions can be called up here.   In events that require immediate attention, such as a manual upshift or loss of oil pressure, the entire display switches to red.  

Above the center vents is the screen, which varies in size based on options, and hides below the dash when the car is off or you turn it off.   Direct sunlight may wash it out and polarized sunglasses may make some info difficult to read (problems not exclusive to Mercedes) but the screen is very close to the line of sight without interfering with it; some of the vision issues are overcome by using the speedometer display for route following.  

Audio controls are below the vents, along with the 10-key pad for the COMAND system.   COMAND is the Mercedes system for controlling the telephone, navigation system, and audio system.   Below that are switches for the rear window shade, seat heaters and other ancillary systems.   At the bottom of the panel is the standard dual-zone climate control, so you needn't fumble through COMAND menus to warm or cool the cabin.   The COMAND system includes an auxiliary input for iPods, and the Multimedia package plays CD, DVD, and memory-card source material. The harman/kardon 5.1 Surround Sound system features 450 watts to drive 12 speakers, and makes the best of all of them with good sound and plenty of impact.   We like the large round controller that moves a needle across the radio tuning display screen just as an old radio dial with vertical pointer gliding left and right.  

The auto shifter solves the dilemma about whether the up/down shift direction should be forward/backward respectively or vice-versa by making downshifts to the left and upshifts to the right.   Automatics offer multiple modes requiring nothing more than a button push or holding the lever left or right for one second; it's a simple setup many could do well to emulate.  

Under the driver's right arm are clamshell-opening armrests and the controller that's become the de facto computer mouse in modern premium cars.   With just a few buttons and a click/rotate wheel it can execute a wide variety of commands, and while the system may not be as intuitive as the benchmarks it's far better than employing 200 buttons to do the same thing.   When pressed we'd label it better than BMW's 2008-or-older iDrive and not quite up to Audi's MMI but these are akin to Mac vs.   PC decisions best left to individual owners.   Do, however, have someone else do a test drive so you can see which commands can be done, and how easily, while the vehicle is in motion.  

As in most compact sedans rear-seat legroom is likely the defining measurement because it's fine for kids and smaller adults but perhaps not the best for need-impressing clients or big golf buddies.   Size aside, those riders do get a nicely shaped and proportioned seat, reading lights, door pockets, comfy center armrest and AC vents; available on most C-Class models are a folding 60/40 rear seat and rear window shade.  

Driver visibility is very good, especially on cars with the bi-Xenon headlamps, although by compact sedan standards the side mirrors are relatively large and shorter drivers may find themselves having to peer around sometimes.   There are three rear headrests but they don't obscure rear vision.  

Trunk space amounts to about 12 cubic feet, adequate but not class-leading.   Load height is reasonable and the well isn't too deep so you won't need a crane to unload overstuffed suitcases.