Before you buy this game be sure to look around first. Many users have reported game breaking bugs such as: Crashing at inventory, falling through the floor as well as It crashing on startup.
Furthermore people are experiencing moderate to severe Framerate issues even on PCs with some of the most powerful hardware available such as the GTX 980.
To be true not everyone has problems and there are those who enjoy what Ubisoft have done with Unity.
Others dislike the changes to the stealth system, guard A.I and the addition of SINGLEPLAYER microtransactions.
So again do some research and look at the various reviews on the web. Although if you do this pay more heed to the player reviews than the critics review especially when researching performance.