This season of Arrow is all about Team Arrow, vs dark magic, in the form of Damien Dhark, played by the great character villain Neal McDonough. As has been the tradition of Arrow and Flash they took a comic book character and added to it, in this case giving Dhark magic power through a totem, and as a result he becomes one of the most powerful opponents for the team ever. There are also tie backs to the prior season with Malcolm now the head of the League of Assassins, resolving the Sara Lance story line (with help from Constantine), as well as the effects of the Lazarus Pit on Thea. Oliver and Felicity start out happy and content with their new non-vigilante life after riding off into the sunset, but that is cut short by Dhark's attempts to take down Star City.
Of course there is also the major death that is hinted at from the very first episode. I will not spoil it for those who do not know, but the show goes out of its way to make sure we know the death is permanent (which given all the back from the dead moments the show has had in its run is something). However given that it exists in a universe where The Flash and Legends of Tomorrow (and even Arrow to some extent because of the flashbacks) play with time, and the fact that the actor whose character was killed off reportedly has a contract to be a series regular across all the DC Universe shows (now presumably including Supergirl), we should see a different incarnation of the character. While I think the suspense of the reveal of the death was better than the actual execution of it, it did make for a lot of touching moments toward the end of the season.
The flashbacks this season again revolve around the island, and this time the reveal of the magic totem that Dhark ends up using in the present. There are no Slade Wilson sightings this year, and one cameo from Shado, but that is it for the prior seasons flashback characters. It is an okay story, but not as strong as the prior flashback stories we have seen, and still no indication of what lead up to Oliver's rescue in season 1.
For those who get the blu-rays, the show looks and sounds great again. There is still no play all option, so if you stop watching you have to find your place again. For extras there are deleted scenes for many episodes, a gag reel, part of the comic con panel discussion, the crossover Flash Episode, and a couple features on the new characters from the crossover which lead to Legends of Tomorrow's plot. There is also a short feature on the character of Damien Dhark and what they wanted to do with him in the show vs the comics. Good for what is there. Also, like with season 3, you are just paying for the blu-rays and not having to get DVDs included as well.
Most people likely know where they stand on the show by now. While I do not think it is necessarily as strong as prior seasons have been, it was solid. They continue to develop characters, as well as add new ones to the mix, and while there is no big cliffhanger this season, the team is in disarray by the end, so many people will be interested to see where they take the story from here.