I wanted a vehicle that was small enough to fit in my garage, has strong towing capability for its size, can handle snow and some dirt roads. The GLK250 was at the high end of the price range I was considering, but the build quality reflects the price. Great seats, great engine, great transmission. Minus points: Small cargo area (but if the vehicle was longer it wouldn't fit in my garage). Upright windshield results in a bit of wind noise. Handling feels "heavy" at first but you get used to it and at German-type highway speeds (above 80 mph) it seems tuned just right.
I average 32 to 33 mpg in combined city/highway driving. Diesel engine has great pulling power. Towed a 2500 pound glider trailer from California to Idaho and back and it pulled up mountain grades on Interstate 80 at 65 mph in 7th gear. Also averaged over 30 mpg while towing.
Something to reduce wind noise around the A pillars. Add vortex generators?
NAV system is OK, but not great. Google maps on my phone does a better job.