As you probably know already, Arrow is about vigilante Oliver Queen and his team of friends tacking down criminals in their city. Now, Arrow is known for it's mystery, season one had a twist in almost every episode, but for some reason this season seemed to loose that. It didn't really have much for you to try and figure out at all. There was sort of an on-going case to begin with where they had to solve a murder but that was resolved before even mid-season. Mostly it was your bad guy-of-the-week format and then a story arc involving new villian Ra's al Ghul, which was OK and entertaining enough, just no mysteries which is what made Arrow so good.
Of course every season has lengthy flashbacks to five years in the past to see what Oliver was up to while away from Starling City, and this time instead of being on a cool island...he's in Hong Kong. After watching the the full season, I definitely preferred when he was on the island, this just didn't seem as interesting and by the end it only amounted to a weak connection to the present day events of the final episode.
Other than that, Arrow continued to be action packed, have awesome characters and this time it was fun catching all the references to The Flash and the like.