A decent expansion, nothing more nothing less.
Balance of Power's campaign focuses on an Imperial Task Force hunting down a Rebel fleet. You can choose to fight for either the Rebels or Imperials, but both campaigns are equally difficult alone. There are often missions that can be impossible by yourself for on reason or another, usually because your team mates do not inspect before destroying. This is irritating because the campaigns are next to impossible without other players meaning that despite the addition of a campaign, XvT is still not single player friendly. Some interesting new additions are the B-Wing, a new Rebel starfighter for the campaign and other game modes, and the Super Star Destroyer in the campaign.
Balance of Power is a decent expansion, it adds a campaign but it is still multiplayer-centric. The addition of the B-Wing and Super Star Destroyer are okay, but that doesn't fix my initial gripes with XvT. Balance of Power is not really worth trying out if you're looking for a single player campaign, you're better off sticking with X-Wing, TIE Fighter, or even X-Wing Alliance.