I have owned this car for about 13 months and put almost 23,000 miles on it. I have loved the experience so far and have had no issues with reliability. Live in CT and the car has been awesome commuting in the snow with the factory tires. Much cooler/rarer than the BMW X3. GLK's faux leather is textured to replicate real leather and has verisimilitude in its touch. Also great with rain, snow, etc. The sound of the doors closing is truly like that of a vault. Unfortunately a wayward deer head-butted my door while I was going 30 mph...but there was NO dent/damage whatsoever! Truly an incredible machine and I am so happy I chose it.
Reliability. Drives incredibly smoothly. Eco-stop is seamless and you get used to it quickly. Getting same mpg as on my 2007 VW Rabbit (about 23+ combined).
Definitely turns heads/makes an awesome first impression. Black on black with black ash wood trim is incredibly elegant. Auto wipers sense intensity of rain perfectly. LEDs below the headlights look awesome, even during the day.
The only possible improvements I could suggest would be to include a single-zone button on the climate control, to position the open buttons for the center console closer to the front of the console for easier access when the seat is closer to steering wheel, and to use an easier/more elegant way to put windshield wipers up in the snow rather than having to turn the car off mid-swipe (see audi/vw).