It might be a slight exaggeration to say that everyone in the world is looking forward to Star Wars: the Old Republic... but only slight. With the latest class reveal, the Imperial Agent is poised to give an excellent sneak-and-snipe playstyle to the Sith side of the game. All well and good... but as Kill Ten Rats notes, how is this game going to get any PvP balance? To the best of everyone's knowledge there's no equivalent ability in the Smuggler's arsenal, the Republic's counterpoint to the Agent, and it's not much of a matchup when one side is invisible and the other side isn't.
Overly Positive recently made a few observations regarding the class balance, noting that BioWare seems to be taking an approach a la Warhammer Online -- each class has a loose equivalent on the other side, but they don't result in being direct copies of one another. However, the downside to this approach is that you can easily wind up with one side's class being overpowered in relation to the other. Direct equivalencies leech some of the flavor, but they ensure that the game remains perfectly balanced for both factions. It's a question worth considering and keeping an eye on as the game moves through development -- after all, if a Jedi and a Sith Warrior can't face off in fair combat, it'll be a sad day for many players.