I have had these tires about 3 weeks, and in that time I've been able to test them in snow, slush, mud and today, ice. ]I've yet to see a review of these tires, so... here's mine.
First of all, my MPG hasn't suffered. In fact, with the warmer weather at the beginning of the week, I was averaging close to 40 MPG, which is higher than I was getting with the Bridgestones when it was warm out!

Snow: handled well going up and down hills and plowing through a half foot of snow in my parents driveway. Got a little scary going 40 on the unplowed interstate when I got passed by a tandem tractor trailer... but hey, that's scary to me when the road is dry, too!!

Slush: I irritate my boyfriend by aiming for mounds of slush in the road. The tires plow through them like a champ, the traction control has yet to come on.

Mud: eh, well, I don't really go off-roading with the car, but my driveway did get a little muddy when it was warm this week and all the snow melted. No problems there either... except the tread got full of mud and left dirt clumps for a half mile down the road... I could hear it thumpthumpthump-ing on the undercarriage

Ice: Had my first experience with tire-on-ice action today. It was freezing rain on my way to work this morning and the tires made it feel like I was glued to the road.

I've tried to force the car into a skid numerous times and only succeeded once, making a left turn in 3 inches of wet snow/slush, and even then it only skidded maybe a foot???

The only problem I encountered with the tires happened when I parked too far down on my driveway (which is like a 45° incline) and it snowed 3"-4" on top of ice. The tires just spun and spun and I eventually ended up having to use cardboard boxes to get enough traction to get out of the driveway. (I'm sure the neighbors had a blast watching me do that, haha)

Also, the tires do have a tendency to "sing" at all speeds. But I'll put up with that if it means I won't end up stuck in the driveway or wrapped around a telephone pole.

So, in all they are a decent, more cost-effective alternative to Nokian Hakkapeliittas. I paid $90/tire for these and was quoted $140/tire for Hakkapeliittas.