The Surly Lou was designed to be used with super wide rims including the Clown Shoe. Together with the Bud, the two were designed to work as a front and rear pair. The massive foot print and aggressive tread allow you to hit the gnarlies...
Strengths: Traction, traction, did I say traction. Awesome float on soft snow.
Weaknesses: cost, rolling resistance is a trade off for great traction.
this rear tire is fantastic, I could climb every hill that others could not. Build confidence going down hills as well. Braking in snow is also really good when a downed tree is on a down hill. My only complaint is that it is $170 a piece. I also have the Bud for the front and they are great together. Surly really did bring out a great product and I am enjoying these tires in the snow.