As a long-term AC fan, I was always going to buy this, but it's nice to see generally good scores.
The way AC games are developed (they overlap), there won't be any major, groundbreaking changes until next year at the earliest. If you enjoy AC games, looks like Syndicate is a good time, and runs a lot better than Unity. If you don't enjoy AC games, I doubt this one will change your mind.
No game is perfect, and Ubi gets a silly amount of flak. I played Unity a month after launch and it was fine. Frame rate could have been a bit better, but I didn't get many glitches at all in over 50h, and certainly nothing game-breaking.
Personally, I love everything AC and, as a Londoner, I can't wait to play Syndicate.