In addition to allowing some heat dissipation through the BSS lines, they also give a better, more solid feel to braking since they don't expand like rubber lines do thus you won't feel your brakes getting spongy as they heat up.
If you want a nice upgrade, especially you guys who've boosted your power, try the Racing Brake 2-piece drilled/slotted rotors. Besides being 6 lbs lighter than the stock rotors, they do a great job of ventilating and dissipating heat. And they look seriously cool too.
Here's how they look on my car (these are the fronts):