Fast, fun-to-drive, small and VERY comfortable.
09 X3 was practically falling apart at 58,000 miles, but GLK is essentially a tall C-Class, which are extremely reliable.
X3 also had mediocre front seats, while GLK uses C Class seats, which are outstanding for even long distance.
The car is also smooth and quiet, with handling that again feels more like a C Class sedan than an SUV.
4Matic all-wheel-drive, "tall C-Class" interior and driving dynamics.
Modernize the electronics to match the latest 2012 C Class sedan.
Uses the same audio and dash electronics as my old 2009 C300, including the iPod cable that only charges older iPods (adapter can allow charging of modern iPod/iPhone).