Lets start with the fact you can't see your feet. Its a simple thing but so few games do it. It does make me wonder if first person games would have people believe everyone is just two disembodied hands.
There's no voice, it was a point Rob made over and over again and I've got to say he's won me over. It doesn't make any sense that Corvo has no voice, characters will talk to him and he wont reply, he'll drop from a large height or get stabbed in the face and wont utter a single sound and at no point is it mentioned he can't actually talk.
Now we've had Rob's big problem, its time for mine, at no point in the game can you look in a mirror or go into third person to see how cool Corvo looks and this distances the gamer from the character their playing.
One of the other big problems with the game is that its short, its only nine missions long, so you don't really have time to relish your powers and upgrades and the story doesn't have enough time to grow.
No New Game Plus
A big problem both me and Rob had was the fact that there's no playthrough plus, so all your hard earned powers and upgrades just disappear, for me this just destroyed most of the replay value the game had and made the fact the game is so short even worse. A point that joins in with the playthrough plus is that when replaying single missions theres no way to buy items or upgrades from Piero, so you can't even restock and upgrade before you replay a mission.
And lastly the biggest problem with Dishonored is the story. The story is really predictable and as the games so short theres not even time to flesh the story out so its just a basic framework rather than a proper storyline.
Dishonored could have easily been the best game of the year hands down, but because of all these mistakes that could have been easily changed the game is left lackluster and annoyingly close to awesome. This is what the "What game's need" posts are for, just to point out how with just a few small changes so many games could become so much better.