If you are on the fence about trying to decide which class to play, try the imperial agent. I have heard over and over again that this class has the best story by far. It seems as if Bioware had a lot of fun writing the story line for this class.
I’ve personally only dabbled a bit with the class (the cover system is not to my liking), but from what I’ve seen so far, it is a very entertaining storyline. I’ve also seen numerous people post that of all of the classes they have tried, this one was the best story hands down.