On paper, the Vision CLS seems like a fairly bright idea, combining the swept lines of a true grand-touring coupe with the practicality of a bona fide luxury sedan. In the flesh, however, it's a bit of a head-scratcher. Just like the big CL-class coupe, the Vision CLS seats four in comfort, but, just like the S-class sedan, it gives back-seaters their own front-hinged, er, doors ("access hatches" seems a better descriptor). Unfortunately, it can't touch the gorgeous lines of the B-pillarless CL and it's not nearly as commodious as an S-class. Under the hood resides a 265-horsepower diesel engine matched to Mercedes' new 7G-Tronic seven-speed automatic transmission. Let's see: Unpretty, unpractical, and diesel-powered. Don't hold your breath for this one, America.