Just beaten this, thoughts below:
+Great graphics IMO, generally suits the setting
+Decent performance considering the age of my graphics card, it only really seems to tail off when there is a lot of foliage around like on that southern island
+Quite a lot of content, it took me 28hrs to beat with 79% completion.
+Works quite well as an open world game, travel doesn't take too long and plenty to get involved in on the way to places
+Level design OK for the most part, not quite so many annoying repetitive sections like in some of the earlier games where failing a jump means a two minute slog to get back to where you were. I think the series has settled into a fairly easy-going parkour vibe now, promoting speed and splendour over taxing platform sections (which is great for someone like me that doesn't like platformers)
+Some good characters, particularly your sidekicks
+Builds well on the naval element introduced in AC3
+Fun the most part, the odd annoying section but given the broad scope of the game acceptable I feel
-Occasional bug where the screen would 'freeze' except that the game is still going on in the background, e.g. the minimap would update/spin as I turned, sound effects playing etc but screen not updating. Mostly seemed to happen at sea.
-Kenway's Fleet is a bit clunky in terms of UX, requiring far too many clicks. E.g. for naval battles it would be nice to be able to have a pre-selected war fleet rather than having to manually cycle through and choose each ship for each slot
-Compounded by the 'decay' on routes being far too rapid, once I'd established 10 routes or so it became like a full time job having to keep going back every hour to get routes back down to green
-Further annoyance with the mobile app - while I commend the innovation, requiring an always-on internet connection is a bit stupid for a mobile game, as by definition it will usually be played when out and about (I kept disconnecting when playing on the train). Again this is compounded by a bug after reconnection where it sometimes claims you already have Kenway's Fleet running on another device, when I don't
-Storm conditions etc are under utilised - there is like a tutorial near the start where you learn how to tackle rogue waves, typhoons etc but you hardly ever encounter them
-Blowpipe feels a bit overpowered, in the sense that it makes stealth sections much easier. There's not enough transition from tough stealth to easy stealth, it just does it in one fell swoop
-Despite what I said about characters, the baddies are a bit lacklustre. Most of them, such as Torres, it was difficult to build up much emotion towards, they were just a bit 'meh'.
-End battle is kind of a let down, other boss fights were better
-Annoying icons on the map that you sail over to, only to find they can't be accessed yet. I think they should have made the Diving Bell available earlier to avoid this.
-Might have just been down to my playstyle but I found I was always short of metal resources. I finished the game with plenty of Jackdraw upgrades not done due to this.
-Upgrading the pirates hideout seemed a bit pointless in general, didn't seem to have as much character as the homestead missions in AC3
-Overall story plot isn't great, certainly not a patch on the Ezio games. Thankfully as mentioned it does compensate for this by being a good open world game
