Gustav is churning in the Caribbean, and poised to get stronger. It is threatening Haiti, which will see strong wind and torrential rain. Flooding will likely cause a lot of damage and threaten lives on the island. Warm water and a favorable upper level wind pattern ( no wind shear to tear it apart ), will likely make Gustav a nasty storm before it is all said and done. That's just in the Caribbean. Hard to tell what Gustav will do late in the forecast period. However, it could emerge in the Southern Gulf of Mexico in the next several days and eventually threaten the US. Too early to tell, but Gustav is going to be one to watch.
Check out the following link for the official track:
Notice the very broad pattern, by day five. That depicts the uncertainty in the long range forecast for Gustav.