I'm on my third set of factory rotors and, once I'm out from warranty, will likely move to Performance Friction Direct Drive rotors from Bimmerworld.
Because it's a true floating rotor design (unlike the stock pieces), upfront cost is a little higher. But the rotor costs are comparable.
I also expect that they'll stand up to track use far better than the stock rotors and have significantly longer life.
BTW, I'm already running front brake rotor cooling ducts.