I bought this game at launch, played through it, traded it in and have since bought it again, traded it in and then bought it again never once completing it a second time. I have the Knife of Dunwall too.
It's like each other time Ive bought it I falsely convince myself it really isnt as boring as it is.
Then I get home, pop it in for about 45 minutes and realize that it really is that boring. Maybe some day Ill come to and play it again in different way or revisit the masquerade party (which was indubitably the best scene of the entire experience).