It's the patch that could end up making all the difference.
Ubisoft has announced that "Patch 4" for Assassin's Creed Unity will release next week across all platforms.
It'll be ready to go on Monday, December 15 and this update will address a laundry list of lingering issues, and will enhance performance, stability, online matchmaking, and general connectivity. The previous patches also worked to handle stability and performance problems, so by the time the fourth patch is installed, Unity should be a much smoother and less frustrating experience.
Personally, I've only run into a very small percentage of the problems I've seen reported but I imagine it varies greatly from person to person. Me, I'm too interested in upping my character and enjoying Paris.