A fairly fun game, with a pretty decent plot, that can good or bad, depending on whether you played its predecessors.
This game most certainly has two faces. If you played Explorers of Time or Explorers of Darkness you will probably be a bit disappointed, as this game is simply those two in disguise (and a bad disguise at that). There are some new features, but they're hardly groundbreaking: Special Missions (where you play a brief story as a different Pokemon from the guild), the interesting and lively but ultimately inconsequential Spinda's cafe and the fun but forgettable mission to Sky Peak. I'm not trying to say that people familiar with Time and Darkness wont have fun playing this, they may well do, especially considering the new starter Pokemon on offer (namely Riolu, Shinx, Vulpix, Phanpy and Eevee) which can give the game a new twist. What I am saying is that veteran players will probably find this game a bit boring, due to it being almost exactly the same as its predecessors.
If you haven't played Time or Darkness, get Explorers of Sky and you will enjoy it immensely, due to its fun graphics, interesting storyline and easy to grasp game play. If you have played Time and Darkness its still worth a look, but don't expect to be dazzled by originality.