I worried that Black Flag would have the same problems that plagued ACIII. Incomplete story arcs, pointless characters, murky mechanics that offer little reward for effort (I'm looking at you, homestead). With only a year between releases, I felt certain that Assassin's creed was to become another Call of Duty, with yearly releases and a loss of quality a certainty.
The truth is, Black Flag is a very enjoyable game. The open world Caribbean is a lot of fun to navigate, with gorgeous vistas and tons of activity. I've stalled the main story for now and am just cruising around the islands, looking for more ships to fight and bases to liberate. The story is a great deal more interesting, though I'm far more excited by the ship combat than the modern day parts. Happily, those are easily skipped this time.
Unfortunately, there are still a few technical issues with the game. Ubisoft has said repeatedly how they've pushed the free-running navigation to it's limits. They tout it as a point of pride, but it's clear the existing tech has been pushed as far as it will go. Early entries in the Assassin's Creed series would transfer easily between running, jumping and climbing, but ACIII and Black Flag both suffer from poor mapping of climbable surfaces. Countless times I've attempted to leap to the next ledge, only to vault off into open air before crashing at the feet of my pursuers or ended up squatting over the treasure box I was trying to loot.
The crafting system is mostly borrowed from Farcry 3. You kill and skin various animals to make better holsters, armor and pouches for your materials. The ship (who shall remain nameless) can be upgraded as well, with the on major difference being the use of wood and metal instead of animal hides.
So far, Assassin's Creed IV; Black Flag is a welcome addition to the series. The huge variety of encounters and possibilities make it more replayable than any other game in the series. I can't call it my favorite in the series (Assassin's Creed II still holds that title), though it comes damn close with it's collectible shanties.
It's foolish to expect any game to be perfect. While Black Flag stumbles in some of the same areas as it's predecessor, it gets so much more right. From the look, sound and feel of the era to the deep open world and it's massive number of secrets and collectibles, Black Flag offers more than enough to keep it afloat.