if you play on PC nvidia released new drivers today to optimize ac4
ninja edit: been running release version of AC4, exactly the same thing as the leaked asian version from last week, doing a windiff at the moment with both versions installed. The PS4 version is superior, the PC version has lots of screen tearing problems and FPS drops and wonky input issues, and I see people on reddit complaining about crashing. Graphically they are pretty much identical, I see no real difference but the engine is pretty crappy so its not a surprise.
multiplayer does have some crafting components, like build weapons and gear from shit you find I think in sp (not sure about this), so probably better to stick to just 1 platform. The multiplayer is fun at launch but pretty dead a few weeks out, especially on PC.