When I heard SAO was getting a second season, I was excited. Yes, SAO is one of my favorite animes, but I try not to let that cloud my judgement for how I would score it.
As you can read in the series description, a player of a shooter VRMMO is killing people in the game. This is the first arc (Phantom Bullet). Kirito gets sent into the game because he's apparently the closest thing to a professional gamer at the disposal of the company trying to solve the mystery of how the player is killing people. Sinon is a sniper in that same game and she's trying to overcome some trauma from her past by 'becoming strong' in the game. It felt a bit drawn out at times, but it still kept me interested as I waited to see how the arc would end.
The second arc (Caliber) is more of a filler arc than anything. Kirito and his harem go on a quest to get excalibur in ALO that takes three episodes. It was a fun little adventure, but it didn't expand the characters in any way, and the overall quest itself was a bit of an odd draw on Norse mythos.
The third arc (Mother's Rosario) involves Asuna taking the role of MC and going on an adventure with a new group of characters, namely Yuuki, to try and clear a New Aincrad floor before anyone else. It was a lot of fun to watch, with plenty of sword art sword play and the new group, the Sleeping Knights guild, had a secret that made me care a bit about them (I think I cared about the Sleeping Knights more than I cared about the majority of Kirito's harem).
The main things I love about SAO return in its second season. The music sounds fantastic and the art is amazing. Not much more needs to be said there.
The usual shortcoming of SAO is its characters, and its second season isn't really an exception. The third arc has Asuna trying to face her own weakness in the real world compared to her strength in VRMMOs, but it's kind of a side-note to the story. Most of the attempts at character development are seen in the first arc. Kirito finally starts to deal with the trauma that comes with the fact that he killed people in Sword Art Online, but that's about it for his character. Sinon, the other MC for the first arc, is given more depth as she tries to come to terms with her own past. However, her interesting character is practically dismissed in order to turn her into the missing tsundere component of Kirito's harem, which was rather disappointing to see. She was a strong character who was reduced to a mess when her trauma followed her into the game, leading her to completely rely on Kirito in the most tsundere ways she could.
I wasn't really a fan of how much of a prodigy Kirito became out of nowhere in this season. Hacking SAO itself back in season one to save Yui wasn't enough to prove his technology prowess; he now makes little cameras that make it so game characters can see the real world without any difficulty whatsoever. The only explanation given to his mechanical genius is that he has been on the internet.
Even though I was REALLY disappointed to see Sinon merge into Kirito's harem without a second thought, it was still a fun season to watch. The art and sound still kept the scenes alive for me and I managed to forgive the shortcomings in the characters and story just because I was still having fun. It may have been ridiculous, but it was fun watching Kirito basically turn into a jedi to deflect bullets in a shooter game.
It's still SAO. Kirito has his harem and still cares for Asuna. Sinon unfortunately becomes a part of the harem, but had a good char before that. Art and Sound still carry the show past its shortcomings for me.