I really enjoy my time with this game... too bad it seems to be underperforming, it's great fun to play through. The design of the game is glorious: the outfits, the painterly look of Victorian London, the character faces, the weather and lighting.
If I had Ubisoft's ear, I'd really like to make these suggestions:
Traversal:
The grappling hook is a wonderful addition. It really improves the flow of moving through the city. But for the love of god, don't make every parkour and grapple move dependent on being right up to the edge of something. Just let me jump and grapple wherever I want...
It's especially annoying when you combine it with the 'teetering on the brink'-animation that triggers whenever your at an edge... completely messes up the sense of flow: you're required to walk right up to an edge for context-sensitive grappling or jumping but if you sprint into it, you lose character control for 2 seconds while they teeter. Holy hell, that gets old fast.
Also, when I'm holding the 'go down' button, actually let my character descend no matter which way the camera is pointed... the game keeps second-guessing my direction of travel - in what situation would a player ever go down the side of a building for two seconds holding the 'go down'-button and then reverse direction back up without pushing any other button? Yet this happens all the time when your character descends past the 'camera angle' and you're looking up at the building while descending.
Thirdly, let grapple in the direction I'm looking at. Always. When I'm staring at a roof in the distance and press grapple, I don't expect the hook to shoot behind me and yank me up a chimney I wasn't even looking at.
Damn it, Ubisoft: you almost nailed it. Almost.
Looting / Crafting:
Okay, this has been bugging me since Black Flag: just give us a full-blown loot and treasure system already. Opening chests and finding collectibles is so incredibly tedious and unexciting - it's always money + crafting material 1 + crafting material 2. The crafting is so meaningless, I never once kept track of how much leather, metal and whatever I had. I just mindlessly pressed the craft button whenever an anvil turned black. That's not crafting, that's like playing Farmville.
Save the crafting for upgrades. Make opening chests exciting and rewarding: let us find gear, weapons and flair-items, maybe even at random. Staring at lists and tables is not exciting: climbing into an attic and finding a hidden chest with a unique hood is.
Stop reducing every bit of open-world exploration to 'filling a meter' for a reward.