I think there's a bug on the last level. Are you supposed to be able to walk up the stairs? I couldn't figure out another way around and that didn't work.
Otherwise though, really nice game. A lot of content - I liked the pushing boxes to block the guards, and how the noisiness of your guys is important.
Was there any thought to having ranged combat? I think if guards were shooting then it would have added another spin, choosing which guards to approach.