I just finished the book and this has been bugging me.
Han Solo was right. The "Kessel Run" refers to driving a ship through the "Maw Black Hole Cluster." Since the area is full of black holes, you have to steer well clear, increasing the distance. What Solo was refering to was the "shortest distance," which Lucas has stated on the DVD commentary, implies an extremely fast and powerful ship since he can run closer to black holes (hence a straighter, shorter path) without the risk of being caught in it's gravity.
The shortest distance through a Kessel Run means you've got a fast and powerful ship.
Or was that too much geek.