The gameplay was improved, but the storyline is mainly why I play these games, and this did nothing for me. People always bury AC3 for it's obvious flaws, but I managed to semi-enjoy it because I found the setting and the historical figures in the game interesting.
With Unity, the only historical figure that peaked any interest of mine was Napoleon. He does quietly obtain something of note, but it's more a cameo and a nod to long time AC players that know the lore of the series; his actual role in Unity's story is limited at best.
I honestly felt like I was going through the motions, and just kept going because I was hoping that there would be some sort of payoff in the end, even if it was another classic AC cliffhanger ending. We didn't even get that, it just ended, and the plot never advanced at any point during the game. Anyone can finish Black Flag, skip Unity outright, and play Victory when it releases this November and we would all be on the same page as far as the story is concerned.
I think the most enjoyable thing that I took away from it was the absurd amount of hilarious glitches that I captured via game DVR. I may upload them all to YouTube tonight and share them with you guys because some of them are gems, and things that I never expected to encounter while playing a game.