I traded my 08 CTS4 and never looked back. Both vehicles had the same price. I just wished the GLK was out then. Owning mostly GM vehicles, my deciding factor was the availability of Teleaid. It's like power windows, once you have it you never go back. There are so many things to love about this vehicle, especially the ride. After driving the C Class, I'm amazed that they are even relatives. I averaged 21.8 mpg today on a 257 mile trip, with a 1600 ft climb (love the altimiter), head winds and averaging 70 to 80 mph. My 24 mile city loop to work averages 19. I don't think that is bad for 2 tons of fun! Biggest Gripe: No A/T tires available for 19's on a AWD.
Driving position is great with dead pedal placed right. Great lighting w/ LED pkg. The quiet and supple ride. The Nav is good, not as good as the CTS, but the altimiter/Lat/Long adds to the fun quotient. H/K sound sys is great. Front cup holders well thought out. The heated seats stay on now.
Cell phone holder under front rest too small by todays standards. You should be able to crack the sunroof without having to move the shade all the way back. A/C controls are difficult to see with dark polarized glasses. Storage could be better. The glove box shelf should be canted so items stay put.