Finished off the main story for Assassin's Creed: Unity yesterday (and a bunch of the side missions, but not all of them - there's a stack, not sure if I'll do them all, but plan to do a few more before I'm done with the game for good) and thought it was very enjoyable and well put together

. Which, given the initial reception it got, suggests it got some serious patching! The story held up pretty well, and there were dedicated 'Assassination' missions, which were an improvement for the series - as was the 'press button to tell game whether you wanted to free run up or down'. Traversal wasn't still perfect, there were more than a few moments when it felt like I was wrestling with the controls to get the Arno (the main character) to do what I'd like, but it was a step up on previous iterations of the game. Generally speaking, the gameplay was 'similar but improved' on the past, and was as enjoyable as ever to me, but wouldn't be likely to bring over people that hadn't enjoyed later last-gen AC games.
I think their biggest mistake in game design was in the setting. I personally really enjoyed the take on 18th century Paris, but the city itself as a setting is a bit limited in scope compared with most previous settings in the series. Even the games that took place in Rome and Constantinople had greater variety in their settings, and definitely in their colouring, and coming after the likes of AC3 and Black Flag, it probably felt a bit limited to some (even though the actual geometric scope and amount of gameplay was huge - took me 40-odd hours to play through what I've done, and I've only played a couple of coop missions and a little over half the side missions). It will be interesting to see if they can make Victorian London a bit more varied.