Not finding a demo at Bethesda, I Googled it. Not only were there a lot of other people asking for a playable demo, some were being given help on alternative, non-legal ways of 'trying it out'. This seems an utter travesty to Arkane, especially given that the game is being sold at a very reasonable price and is a fantastic single-player campaign that deserves the support of those of us who miss good single-player titles. In trying to find a demo, players are instead taken to links that likely won't result in a sale.
Then there are those who won't risk buying something they cannot first try. I'm one of them, and I didn't buy Dishonored because there was no demo. The review I read in my fave magazine was written in a story-style write-up along the lines of: "so I 'blinked across to a balcony, then performed a lethal drop-down before taking possession of the adjacent guard...". Given that I'm not great with a myriad controls, it sounded complex and as my funds are limited, I walked away despite the many glowing magazine reviews.
It was only my total obsession with Thief 3 that finally convinced me take the risk last week. As I near the end of my first play of Dishonored, I am so thankful that I did, and horrified at how I nearly didn't! If there had been a playable demo available (maybe the first two missions - just enough to show off the graphics, the easy controls and an intro to the blink feature), I would have bought it instantly - without a doubt, and I imagine many others would too.
So a plea to Bethesda/Arkane - please consider making a playable demo. A title such as this deserves a massive audience!