Gustav looks like the real deal. A couple of model runs suggest the potential for Cat 4/5 status near Cuba. The waters between Jamaica and Cuba have the highest heat potential in the basin. Less heat potential in the Gulf but waters still capable of sustaining a major (Cat 3+) storm provided inhibiting factors like shear are minimal. My initial thoughts suggested a south-central or southwest LA hit due to a ridge weakness in the wake of Fay but a more southerly track means Gustav could meander further west. Now Port Aurther and Houston will also need to keep close tabs on this system.

Stealing thunder from someone else...
Best hopes for a Kenedy County, TX landfall (as low density as it gets) or a diminished storm elsewhere.