It wasn't made by Bethesda, but by the guys that made the new Batman games. Bethesda just published it.
Nope. Arkane Studios made four games so far:
Arx Fatalis, Dark Messiah of Might and Magic, Bioshock 2 and now Dishonored. The good Batman games were by Rocksteady, iirc
But yeah, Bethesda still published it, and most of their published games are buggy as fuck upon release, whether developed by Obsidian, id or Splash Damage.
The issue I take with non-lethal gameplay is the lack of variety in takedowns. There are so many neat tools for killing enemies.... then again, the Outsider would probably want you to wreak havoc!