In short, they didn't enjoy the feeling of the rather light steering feel and the overall less sporty nature of the car compared to its rivals, while the exterior looks were... gasp!... compared to that of the Honda Accord Coupe.
The high points were found in the smoothness and responsiveness of the soon-to-be replaced 3.5-liter normally aspirated V6 engine, the class-leading interior comfort and - coming as a bit of a surprise – the C350 4Matic Coupe's much lower price than that of its competitors. You can check out their entire review here and you can also have a look at a reasonably exhaustive gallery of the C250 Coupe Sport in US-Spec guise in the adjacent photo gallery.