How is Assassin's Creed 4 Multiplayer?

I'll be picking up AC4 next Friday for my PS4. This will be my first AC experience aside from watching my brother play AC3 last year. Of course, my purchasing decision is mostly weighted on the game's stellar single-player experience, but I am also curious about the multiplier component.

I've watched a few Youtube videos of the mode, and it looks interesting, different and surprisingly fun. I'm just wondering what other gamers think of it. Is multiplayer completely overshadowed by single-player, or does the mode have its own little shiny niche in the AC realm? Does the multiplier community fizzle out after the game's launch window, or does it have longevity?

Is it even fun?